Terminal, base station and signal transmission control method

ABSTRACT

Provided are a terminal, a base station and a signal transmission control method whereby a response signal can be efficiently transmitted when the terminal receives downstream allocation control information via an R-PDCCH. An extraction unit ( 204 ) receives downstream control information via one of a first downstream control channel, which is transmitted by use of one or more control channel elements (CCE) associated with an upstream control channel resource, and a second downstream control channel different from the first downstream control channel, and also receives data via a data channel. A control unit ( 208 ) selects, from resources associated with CCE and from particular resources reported by a base station, an upstream control channel resource to be used in transmission of the response signal, and controls the transmission of the response signal.

TECHNICAL FIELD

The claimed invention relates to a terminal, a base station and a signaltransmission control method.

BACKGROUND ART

3GPP LTE employs Orthogonal Frequency Division Multiple Access (OFDMA)as a downlink communication scheme. In radio communication systems towhich 3GPP LTE is applied, base stations transmit synchronizationsignals (i.e., Synchronization Channel: SCH) and broadcast signals(i.e., Broadcast Channel: BCH) using predetermined communicationresources. Meanwhile, each terminal finds an SCH first and therebyensures synchronization with a base station. Subsequently, the terminalreads BCH information to acquire base station-specific parameters (see,Non-Patent Literatures (hereinafter, abbreviated as NPL) 1, 2 and 3).

In addition, upon completion of the acquisition of the basestation-specific parameters, each terminal sends a connection request tothe base station to thereby establish a communication link with the basestation. The base station transmits control information via PhysicalDownlink Control CHannel (PDCCH) as appropriate to the terminal withwhich a communication link has been established.

The terminal performs “blind-determination” on each of a plurality ofpieces of control information included in the received PDCCH signals(i.e., Downlink (DL) Assignment Control Information: also referred to asDownlink Control Information (DCI)). To put it more specifically, eachpiece of the control information includes a Cyclic Redundancy Check(CRC) part and the base station masks this CRC part by the terminal IDof the transmission target terminal. Accordingly, until the terminaldemasks the CRC part of the received piece of control information withits own terminal ID, the terminal cannot determine whether or not thepiece of control information is intended for the terminal. In thisblind-determination, if the result of demasking the CRC part indicatesthat the CRC operation is OK, the piece of control information isdetermined as being intended for the terminal.

Moreover, in 3GPP LTE, Automatic Repeat Request (ARQ) is applied todownlink data to terminals from a base station. To put it morespecifically, each terminal feeds back response signals indicating theresult of error detection on the downlink data to the base station. Eachterminal performs a CRC on the downlink data and feeds backAcknowledgment (ACK) when CRC=OK (no error) or Negative Acknowledgment(NACK) when CRC=Not OK (error) to the base station as response signals.An uplink control channel such as Physical Uplink Control Channel(PUCCH) is used to feed back the response signals (i.e., ACK/NACKsignals (hereinafter, may be referred to as “A/N,” simply)).

The control information to be transmitted from a base station hereinincludes resource assignment information including information onresources assigned to the terminal by the base station. As describedabove, PDCCH is used to transmit this control information. The PDCCHincludes one or more L1/L2 control channels (L1/L2 CCH). Each L1/L2 CCHconsists of one or more Control Channel Elements (CCE). To put it morespecifically, a CCE is the basic unit used to map the controlinformation to PDCCH. Moreover, when a single L1/L2 CCH consists of aplurality of CCEs (2, 4 or 8), a plurality of contiguous CCEs startingfrom a CCE having an even index are assigned to the L1/L2 CCH. The basestation assigns the L1/L2 CCH to the resource assignment target terminalin accordance with the number of CCEs required for notifying the controlinformation to the resource assignment target terminal. The base stationmaps the control information to physical resources corresponding to theCCEs of the L1/L2 CCH and transmits the mapped control information.

In addition, CCEs are associated with component resources of PUCCH(hereinafter, may be referred to as “PUCCH resource”) in a one-to-onecorrespondence. Accordingly, a terminal that has received an L1/L2 CCHidentifies the component resources of PUCCH that correspond to the CCEsforming the L1/L2 CCH and transmits response signals to the base stationusing the identified resources. However, when the L1/L2 CCH occupies aplurality of contiguous CCEs, the terminal transmits the responsesignals to the base station using a PUCCH component resourcecorresponding to a CCE having a smallest index among the plurality ofPUCCH component resources respectively corresponding to the plurality ofCCEs (i.e., PUCCH component resource associated with a CCE having aneven numbered CCE index). In this manner, the downlink communicationresources are efficiently used.

As illustrated in FIG. 1, a plurality of response signals transmittedfrom a plurality of terminals are spread using a Zero Auto-correlation(ZAC) sequence having the characteristic of zero autocorrelation intime-domain, a Walsh sequence and a discrete Fourier transform (DFT)sequence, and are code-multiplexed in a PUCCH. In FIG. 1, (W0, W1, W2,W3) represent a length-4 Walsh sequence and (F0, F1, F2) represent alength-3 DFT sequence. As illustrated in FIG. 1, ACK or NACK responsesignals are primary-spread over frequency components corresponding to 1SC-FDMA symbol by a ZAC sequence (length-12) in frequency-domain. To putit more specifically, the length-12 ZAC sequence is multiplied by aresponse signal component represented by a complex number. Subsequently,the ZAC sequence serving as the response signals and reference signalsafter the primary-spread is secondary-spread in association with each ofa Walsh sequence (length-4: W0-W3 (may be referred to as Walsh CodeSequence)) and a DFT sequence (length-3: F0-F2). To put it morespecifically, each component of the signals of length-12 (i.e., responsesignals after primary-spread or ZAC sequence serving as referencesignals (i.e., Reference Signal Sequence) is multiplied by eachcomponent of an orthogonal code sequence (i.e., orthogonal sequence:Walsh sequence or DFT sequence). Moreover, the secondary-spread signalsare transformed into signals of length-12 in the time-domain by inversefast Fourier transform (IFFT). A CP is added to each signal obtained byIFFT processing, and the signals of one slot consisting of seven SC-FDMAsymbols are thus formed.

The response signals from different terminals are spread using ZACsequences each corresponding to a different cyclic shift value (i.e.,index) or orthogonal code sequences each corresponding to a differentsequence number (i.e., orthogonal cover index (OC index)). An orthogonalcode sequence is a combination of a Walsh sequence and a DFT sequence.In addition, an orthogonal code sequence is referred to as a block-wisespreading code in some cases. Thus, base stations can demultiplex thecode-multiplexed plurality of response signals using the related artdespreading and correlation processing (see, NPL 4).

However, it is not necessarily true that each terminal succeeds inreceiving downlink assignment control signals because the terminalperforms blind-determination in each subframe to find downlinkassignment control signals intended for the terminal. When the terminalfails to receive the downlink assignment control signals intended forthe terminal on a certain downlink component carrier, the terminal wouldnot even know whether or not there is downlink data intended for theterminal on the downlink component carrier. Accordingly, when a terminalfails to receive the downlink assignment control signals intended forthe terminal on a certain downlink component carrier, the terminalgenerates no response signals for the downlink data on the downlinkcomponent carrier. This error case is defined as discontinuoustransmission of ACK/NACK signals (DTX of response signals) in the sensethat the terminal transmits no response signals.

In 3GPP LTE systems (may be referred to as “LTE system,” hereinafter),base stations assign resources to uplink data and downlink data,independently. For this reason, in the 3GPP LTE system, terminals (i.e.,terminals compliant with LTE system (hereinafter, referred to as “LTEterminal”)) encounter a situation where the terminals need to transmituplink data and response signals for downlink data simultaneously in theuplink. In this situation, the response signals and uplink data from theterminals are transmitted using time-division multiplexing (TDM). Asdescribed above, the single carrier properties of transmission waveformsof the terminals are maintained by the simultaneous transmission ofresponse signals and uplink data using TDM.

In addition, as illustrated in FIG. 2, the response signals (i.e.,“A/N”) transmitted from each terminal partially occupy the resourcesassigned to uplink data (i.e., Physical Uplink Shared CHannel (PUSCH)resources) (i.e., response signals occupy some SC-FDMA symbols adjacentto SC-FDMA symbols to which reference signals (RS) are mapped) and arethereby transmitted to a base station in time-division multiplexing(TDM). In FIG. 2, however, “subcarriers” in the vertical axis of thedrawing are also termed as “virtual subcarriers” or “time contiguoussignals,” and “time contiguous signals” that are collectively inputtedto a discrete Fourier transform (DFT) circuit in a SC-FDMA transmitterare represented as “subcarriers” for convenience. To put it morespecifically, optional data of the uplink data is punctured due to theresponse signals in the PUSCH resources. Accordingly, the quality ofuplink data (e.g., coding gain) is significantly reduced due to thepunctured bits of the coded uplink data. For this reason, base stationsinstruct the terminals to use a very low coding rate and/or to use verylarge transmission power so as to compensate for the reduced quality ofthe uplink data due to the puncturing.

Meanwhile, the standardization of 3GPP LTE-Advanced for realizing fastercommunications than 3GPP LTE has started. 3GPP LTE-Advanced systems (maybe referred to as “LTE-A system,” hereinafter) follow 3GPP LTE systems(may be referred to as “LTE system,” hereinafter). 3GPP LTE-Advanced isexpected to introduce base stations and terminals capable ofcommunicating with each other using a wideband frequency of 40 MHz orgreater to realize a downlink transmission rate up to 1 Gbps or above.

In the LTE-A system, in order to simultaneously achieve backwardcompatibility with the LTE system and ultra-high-speed communicationsseveral times faster than transmission rates in the LTE system, theLTE-A system band is divided into “component carriers” of 20 MHz orbelow, which is the bandwidth supported by the LTE system. In otherwords, the “component carrier” is defined herein as a band having amaximum width of 20 MHz and as the basic unit of communication band.Moreover, “component carrier” in downlink (hereinafter, referred to as“downlink component carrier”) is defined as a band obtained by dividinga band according to downlink frequency bandwidth information in a BCHbroadcasted from a base station or as a band defined by a distributionwidth when a downlink control channel (PDCCH) is distributed in thefrequency domain. In addition, “component carrier” in uplink(hereinafter, referred to as “uplink component carrier”) may be definedas a band obtained by dividing a band according to uplink frequency bandinformation in a BCH broadcasted from a base station or as the basicunit of a communication band of 20 MHz or below including a PhysicalUplink Shared CHannel (PUSCH) in the vicinity of the center of thebandwidth and PUCCHs for LTE on both ends of the band. In addition, theterm “component carrier” may be also referred to as “cell” in English in3GPP LTE-Advanced.

The LTE-A system supports communications using a band obtained byaggregating several component carriers, so called “carrier aggregation.”In general, throughput requirements for uplink are different fromthroughput requirements for downlink. For this reason, so called“asymmetric carrier aggregation” has been also discussed in the LTE-Asystem. In asymmetric carrier aggregation, the number of componentcarriers configured for any terminal compliant with the LTE-A system(hereinafter, referred to as “LTE-A terminal”) differs between uplinkand downlink. In addition, the LTE-A system supports a configuration inwhich the numbers of component carriers are asymmetric between uplinkand downlink, and the component carriers have different frequencybandwidths.

FIG. 3 is a diagram provided for describing asymmetric carrieraggregation and a control sequence applied to individual terminals. FIG.3 illustrates a case where the bandwidths and numbers of componentcarriers are symmetric between the uplink and downlink of base stations.

In FIG. 3, a configuration in which carrier aggregation is performedusing two downlink component carriers and one uplink component carrieron the left is set for terminal 1, while a configuration in which thetwo downlink component carriers identical with those used by terminal 1are used but uplink component carrier on the right is used for uplinkcommunications is set for terminal 2.

Referring to terminal 1, an LTE-A base station and an LTE-A terminalincluded in the LTE-A system transmit and receive signals to and fromeach other in accordance with the sequence diagram illustrated in FIG.3A. As illustrated in FIG. 3A, (1) terminal 1 is synchronized with thedownlink component carrier on the left when starting communications withthe base station and reads information on the uplink component carrierpaired with the downlink component carrier on the left from a broadcastsignal called system information block type 2 (SIB2). (2) Using thisuplink component carrier, terminal 1 starts communications with the basestation by transmitting, for example, a connection request to the basestation. (3) Upon determining that a plurality of downlink componentcarriers need to be assigned to the terminal, the base station instructsthe terminal to add a downlink component carrier. However, in this case,the number of uplink component carriers is not increased, and terminal1, which is an individual terminal, starts asymmetric carrieraggregation.

In addition, in the LTE-A system to which carrier aggregation isapplied, a terminal may receive a plurality of pieces of downlink dataon a plurality of downlink component carriers at a time. In LTE-A,studies have been carried out on channel selection (also referred to as“multiplexing”), bundling and a discrete Fourier transform spreadorthogonal frequency division multiplexing (DFT-S-OFDM) format as amethod of transmitting a plurality of response signals for the pluralityof pieces of downlink data. In channel selection, not only symbol pointsused for response signals, but also the resources to which the responsesignals are mapped are varied in accordance with the pattern of resultsof the error detection on the plurality of pieces of downlink data.Compared with channel selection, in bundling, ACK or NACK signalsgenerated according to the results of error detection on the pluralityof pieces of downlink data are bundled (i.e., bundled by calculating alogical AND of the results of error detection on the plurality of piecesof downlink data, provided that ACK=1 and NACK=0), and response signalsare transmitted using one predetermine resource. In transmission usingthe DFT-S-OFDM format, a terminal jointly encodes (i.e., joint coding)the response signals for the plurality of pieces of downlink data andtransmits the coded data using the format (see, NPL 5).

To put it more specifically, channel selection is a technique thatvaries not only the phase points (i.e., constellation points) of theresponse signals but also the resources used for transmission of theresponse signals on the basis of whether the response signals for theplurality of pieces of downlink data received on the plurality ofdownlink component carriers are ACK or NACK as illustrated in FIG. 4.Meanwhile, bundling is a technique that bundles ACK/NACK signals for theplurality of pieces of downlink data into a single set of signals andthereby transmits the bundled signals using one predetermined resource(see, NPLs 6 and 7).

A description will be herein provided regarding ARQ control usingchannel selection and bundling in a case where asymmetric carrieraggregation is applied to terminals, with reference to FIG. 4.

For example, as illustrated in FIG. 4, when a component carrier groupconsisting of downlink component carriers 1 and 2 and uplink componentcarrier 1 (may be referred to as “component carrier set” in English) isconfigured for terminal 1, downlink resource assignment information isfirst transmitted from a base station to terminal 1 on each of thePDCCHs of respective downlink component carriers 1 and 2, and downlinkdata is then transmitted using the resource corresponding to thedownlink resource assignment information.

In channel selection, when a terminal succeeds in receiving the downlinkdata on component carrier 1 but fails to receive the downlink data oncomponent carrier 2 (i.e., the response signals of component carrier 1are ACK and the response signals of component carrier 2 are NACK), theresponse signals are mapped to a PUCCH resource in PUCCH region 1 and afirst phase point (e.g., the phase point (1,0) and/or the like) is usedas the phase point of the response signals. In addition, when a terminalsucceeds in receiving the downlink data on component carrier 1 andsucceeds in receiving the downlink data on component carrier 2, theresponse signals are mapped to a PUCCH resource in PUCCH region 2 andthe first phase point is used. To put it more specifically, when thereare two downlink component carriers, the results of error detection arerepresented in four patterns, and the four patterns can be representedby the combinations of two resources and two types of phase points.

In bundling, when succeeding in receiving both of the two pieces ofdownlink data (CRC=OK), terminal 1 calculates a logical AND of ACK (=1)for downlink component carrier 1 and ACK (=1) for downlink componentcarrier 2 and transmits the result of calculation, which is “1” (i.e.,ACK), to the base station as bundled ACK/NACK signals. Meanwhile, whensucceeding in receiving the downlink data on downlink component carrier1 but failing to receive the downlink data on downlink component carrier2, terminal 1 calculates a logical AND of ACK (=1) for downlinkcomponent carrier 1 and NACK (=0) for downlink component carrier 2 andtransmits the result of calculation, which is “0” (i.e., NACK), to thebase station as bundled ACK/NACK signals. Likewise, when failing toreceive both of the pieces of downlink data, terminal 1 calculates alogical AND of NACK (=0) and NACK (=0) and feeds back “0” (i.e., NACK)to the base station as bundled ACK/NACK signals.

As described above, in bundling, only when succeeding in receiving allof the plurality of pieces of downlink data transmitted to the terminal,the terminal transmits only one ACK to the base station as bundledACK/NACK signals, and when failing to receive even one piece of downlinkdata, the terminal transmits only one NACK to the base station asbundled ACK/NACK signals. In this manner, the overhead of the uplinkcontrol channels can be reduced. It should be noted that, each terminaltransmits bundled ACK/NACK signals using a PUCCH resource having thelowest frequency or identification number (i.e., index), for example,among the PUCCH resources corresponding to the plurality of CCEs thathave been occupied by the received plurality of downlink controlsignals.

Next, a description will be provided regarding a method of transmittingbundled ACK/NACK signals using the DFT-S-OFDM format with reference toFIG. 5. The coded data obtained by jointly encoding (i.e., joint coding)the response signals for the plurality of pieces of downlink datatransmitted using the DFT-S-OFDM format includes the results of errordetection for the respective downlink component carriers as individualpieces of data. The coded data that is obtained by jointly encoding(i.e., joint coding) the response signals for the plurality of pieces ofdownlink data and that includes the results of error detection for therespective downlink component carriers is hereinafter referred to as“bundled ACK/NACK signals” or “bundled response signals.”

As the reference signals used for demodulating the bundled ACK/NACKsignals, a “length-12 ZAC sequence (i.e., base sequence)” similar to thereference signals in LTE is used. To put it more specifically, alength-12 ZAC sequence is placed on the second and sixth SC-FDMA symbolsand secondary-spread in association with a Walsh sequence (length-2:W′0, W′1). In addition, the spread signals are transformed intotime-domain signals by IFFT. The processing described above isequivalent to the processing in which the signals obtained bytransforming the ZAC sequence into the time-domain signals using IFFTprocessing is spread using a length-2 Walsh sequence.

As in the case of reference signals for ACK/NACK in LTE, the referencesignals from different terminals are spread using sequences eachcorresponding to a different cyclic shift value (i.e., cyclic shiftindex) or a different Walsh sequence. Thus, base stations candemultiplex the plurality of code-multiplexed reference signals usingthe related art despreading and correlation processing.

In the DFT-S-OFDM format illustrated in FIG. 5, a “length-12 ZACsequence” is used as the reference signals as described above. In thiscase, the signals consisting of 12 symbols are subjected to DFTprocessing and then primary-spread in 1 SC-FDMA symbol as bundledACK/NACK signals. As described above, the response signals of one symbolobtained by BPSK modulation are primary-spread in 1 SC-FDMA symbol usinga ZAC sequence (of length-12) in the frequency-domain in the LTE system.In contrast to the LTE system, when a “length-12 ZAC sequence” is usedas the reference signals for reporting bundled ACK/NACK signals usingDFT-S-OFDMA in the LTE-A system to which carrier aggregation is applied,the bundled ACK/NACK signals consisting of 12 symbols are subjected toDFT processing and primary-spread in 1 SC-FDMA symbol. It should benoted that, the bundled ACK/NACK signals consisting of 12 symbolsinclude the results of error detection for the respective componentcarriers as individual pieces of data as described above.

Subsequently, the bundled ACK/NACK signals that have undergone DFTprocessing are placed on the first, third, fourth, fifth and seventhSC-FDMA symbols and spread in association with a DFT sequence (oflength-5: F′0, F′1, F′2, F′3, F′4). Moreover, the spread signals aretransformed into the time-domain signals by IFFT processing. Theprocessing described above is equivalent to the processing in which thesignals obtained by transformation into the time-domain signals usingIFFT processing are multiplied by each component element of the length-5DFT sequence.

The bundled ACK/NACK signals from different terminals arecode-multiplexed herein by spreading the bundled ACK/NACK signals usingdifferent DFT sequences. To put it more specifically, since the bundledACK/NACK signals are spread using the length-5 DFT sequence, bundledACK/NACK signals from as many as five terminals can be code-multiplexed.

In addition, a cyclic prefix (CP) is added to each signal obtained byIFFT processing, and the signals of one slot consisting of seven SC-FDMAsymbols are thus formed.

Hereinafter, the resources adopting the DFT-S-OFDM format structure andused for transmitting the bundled ACK/NACK signals are referred to as“bundled ACK/NACK resource.” As illustrated in FIG. 5, when downlinkdata is transmitted using the DFT-S-OFDM format, the bundled ACK/NACKsignals are placed on the data parts where downlink data is placed(i.e., first, third, fourth, fifth and seventh SC-FDMA symbols in theexample in FIG. 5). In addition, the reference signals for demodulatingthe bundled ACK/NACK signals are time-multiplexed with the bundledACK/NACK signals.

Moreover, the introduction of radio communication relay apparatuses(hereinafter, referred to as “relay station” or “RN: relay node”) is setforth for the purpose of achieving an increase in the coverage in LTE-A(see, FIG. 6). Along with the introduction of relay stations, thestandardization of downlink control channels from base stations to relaystations (hereinafter, referred to as “R-PDCCH”) is in progress (e.g.,see, NPLs 8, 9, 10 and 11). Currently, the following matters on R-PDCCHare discussed. FIG. 7 illustrates R-PDCCH regions.

(1) The mapping start position of an R-PDCCH in the time-domaindirection is fixed to the fourth OFDM symbol from the top OFDM symbol ina single subframe. This position is fixed independently of theproportion of symbols occupied by a PDCCH in the time-domain direction.

(2) As a method of mapping an R-PDCCH in the frequency-domain direction,two assignment methods (i.e., distributed and localized methods) aresupported.

(3) As the reference signals for demodulation, common reference signals(CRS) and demodulation reference signals (DM-RS) are supported. Basestations notify relay stations of which reference signals are used.

CITATION LIST Non-Patent Literature

-   NPL 1-   3GPP TS 36.211 V9.1.0, “Physical Channels and Modulation (Release    9),” May 2010-   NPL 2-   3GPP TS 36.212 V9.2.0, “Multiplexing and channel coding (Release    9),” June 2010-   NPL 3-   3GPP TS 36.213 V9.2.0, “Physical layer procedures (Release 9),” June    2010-   NPL 4-   Seigo Nakao, Tomofumi Takata, Daichi Imamura, and Katsuhiko    Hiramatsu, “Performance enhancement of E-UTRA uplink control channel    in fast fading environments,” Proceeding of IEEE VTC 2009 spring,    April. 2009-   NPL 5    -   Ericsson and S T-Ericsson, “A/N transmission in the uplink for        carrier aggregation,” R1-100909, 3GPP TSG-RAN WG1 #60, February        2010-   NPL 6-   ZTE, 3GPP RAN1 meeting #57, R1-091702, “Uplink Control Channel    Design for LTE-Advanced,” May 2009-   NPL 7-   Panasonic, 3GPP RAN1 meeting #57, R1-091744, “UL ACK/NACK    transmission on PUCCH for Carrier aggregation,” May 2009-   NPL 8-   3GPP TSG RAN WG1 meeting, R1-102700, “Backhaul Control Channel    Design in Downlink,” May 2010-   NPL 9-   3GPP TSG RAN WG1 meeting, R1-102881, “R-PDCCH placement,” May 2010-   NPL 10-   3GPP TSG RAN WG1 meeting, R1-103040, “R-PDCCH search space design”    May 2010-   NPL 11-   3GPP TSG RAN WG1 meeting, R1-103062, “Supporting frequency diversity    and frequency selective R-PDCCH transmissions” May 2010

SUMMARY OF INVENTION Technical Problem

The amount of resources in the resource region where a PDCCH intendedfor terminals served by a base station is mapped (hereinafter, referredto as “PDCCH region”) may become insufficient. As a solution for theshortage of resources, it is thought that downlink assignment controlinformation (i.e., DCI) intended for a terminal served by a base stationis assigned in the abovementioned resource region where an R-PDCCH ismapped (hereinafter, referred to as “R-PDCCH region”) (see, FIG. 8).However, whether the R-PDCCH region is actually used for transmission ofDCI or transmission of normal downlink data is determined for eachsubframe according to scheduling by the base station.

In this case, even when a terminal receives downlink assignment controlinformation via an R-PDCCH and receives downlink data, theabovementioned ARQ is also applied. However, the method of transmittingresponse signals in this case has not been sufficiently discussed yet.

It is an object of the claimed invention to provide a terminal, a basestation and a signal transmission control method that make it possibleto efficiently transmit response signals when a terminal receivesdownlink assignment control information via an R-PDCCH.

Solution to Problem

A terminal according to an aspect of the claimed invention includes: areceiving section that receives downlink control information via one ofa first downlink control channel transmitted by one or a plurality ofcontrol channel elements (CCE) associated with a resource of an uplinkcontrol channel and a second downlink control channel different from thefirst downlink control channel and that receives a piece of data via adata channel; a generation section that generates response signals forthe piece of data on the basis of the presence or absence of an error inthe piece of data; and a control section that controls transmission ofthe response signals by selecting a resource of the uplink controlchannel used for the transmission of the response signals, from aresource associated with the CCE and a specific resource notified by abase station, according to whether the downlink control information isreceived via the first downlink control channel or the second downlinkcontrol channel.

A base station according to an aspect of the claimed invention includes:a transmitting section that transmits downlink control information viaone of a first downlink control channel transmitted by one or aplurality of control channel elements (CCE) associated with a resourceof an uplink control channel and a second downlink control channeldifferent from the first downlink control channel and that transmits apiece of data via a data channel; and a receiving section that selects aresource used for transmission of response signals for the piece of datain a terminal, from a resource associated with the CCE and a specificresource notified to the terminal, according to whether the transmittingsection has transmitted the downlink control information via the firstdownlink control channel or the second downlink control channel and thatreceives the response signals using the selected resource.

A signal transmission control method according to an aspect of theclaimed invention includes: receiving downlink control information viaone of a first downlink control channel associated with a resource of anuplink control channel and a second downlink control channel differentfrom the first downlink control channel, and also receiving a piece ofdata via a data channel; generating response signals for the piece ofdata on the basis of the presence or absence of an error in the piece ofdata; and controlling transmission of the response signals by selectinga resource of the uplink control channel used for the transmission ofthe response signals, from a resource associated with the CCE and aspecific resource notified by a base station, according to whether thedownlink control information is received via the first downlink controlchannel or the second downlink control channel.

Advantageous Effects of Invention

According to the claimed invention, when a terminal receives downlinkassignment control information via an R-PDCCH, response signals can betransmitted efficiently.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram illustrating a method of spreading response signalsand reference signals;

FIG. 2 is a diagram illustrating an operation related to a case whereTDM is applied to response signals and uplink data on PUSCH resources;

FIG. 3 is a diagram provided for describing asymmetric carrieraggregation and a control sequence applied to individual terminals;

FIG. 4 is a diagram provided for describing asymmetric carrieraggregation and a control sequence applied to individual terminals;

FIG. 5 is a diagram provided for describing ARQ control when carrieraggregation is applied to terminals;

FIG. 6 is a diagram provided for describing a communication system thatincludes a radio communication relay apparatus;

FIG. 7 is a diagram illustrating R-PDCCH regions;

FIG. 8 is a diagram provided for describing a mapping example of PDCCH;

FIG. 9 is a block diagram illustrating a main configuration of a basestation according to Embodiment 1 of the claimed invention;

FIG. 10 is a block diagram illustrating a main configuration of aterminal according to Embodiment 1 of the claimed invention;

FIG. 11 is a block diagram illustrating a configuration of the basestation according to Embodiment 1 of the claimed invention;

FIG. 12 is a block diagram illustrating a configuration of the terminalaccording to Embodiment 1 of the claimed invention;

FIG. 13 illustrates control example 1 for A/N resources, according toEmbodiment 1 of the claimed invention;

FIG. 14A illustrates control example 2 for transmission of responsesignals, according to Embodiment 1 of the claimed invention;

FIG. 14B illustrates control example 2 for transmission of responsesignals, according to Embodiment 1 of the claimed invention;

FIG. 15A illustrates control example 3 for transmission of responsesignals, according to Embodiment 1 of the claimed invention;

FIG. 15B illustrates control example 3 for transmission of responsesignals, according to Embodiment 1 of the claimed invention;

FIG. 15C illustrates control example 3 for transmission of responsesignals, according to Embodiment 1 of the claimed invention;

FIG. 15D illustrates control example 3 for transmission of responsesignals, according to Embodiment 1 of the claimed invention;

FIG. 16A illustrates control example 4 for transmission of responsesignals, according to Embodiment 1 of the claimed invention;

FIG. 16B illustrates control example 4 for transmission of responsesignals, according to Embodiment 1 of the claimed invention;

FIG. 16C illustrates control example 4 for transmission of responsesignals, according to Embodiment 1 of the claimed invention;

FIG. 16D illustrates control example 4 for transmission of responsesignals, according to Embodiment 1 of the claimed invention;

FIG. 17 is a block diagram illustrating a terminal according toEmbodiment 2 of the claimed invention; and

FIG. 18 illustrates control example 2 for transmission of responsesignals, according to Embodiment 2 of the claimed invention.

DESCRIPTION OF EMBODIMENTS

Hereinafter, embodiments of the claimed invention will be described indetail with reference to the accompanying drawings. Throughout theembodiments, the same elements are assigned the same reference numeralsand any duplicate description of the elements is omitted.

First of all, before specific configurations and operations of theembodiments are described, a description will be provided regarding amethod to which the inventors of the specification have paid theirattention as a method of transmitting response signals for downlink data(i.e., uplink response signals) when a terminal receives downlinkassignment control information via an R-PDCCH.

The following two methods are considered as a possible method oftransmitting response signals in uplink when a terminal receivesdownlink assignment control information via an R-PDCCH and receivesdownlink data.

One of the methods is to transmit response signals using a PUCCHresource associated in a one-to-one correspondence with a relay-controlchannel element (R-CCE) that has been occupied by an R-PDCCH (i.e.,implicit signaling) (hereinafter, method 1) as in the case of anassociation between a PUCCH resource and a CCE that has been occupied bya PDCCH in LTE. To put it more specifically, when DCI intended for aterminal served by a base station is placed in an R-PDCCH region, eachR-PDCCH occupies a resource consisting of one or a plurality ofcontiguous R-CCEs as in the case of PDCCHs. In addition, as the numberof R-CCEs occupied by an R-PDCCH (i.e., the number of aggregated CCEs:relay CCE aggregation level), one of aggregation levels 1, 2, 4 and 8 isselected in accordance with the number of information bits of theassignment control information or a propagation path condition of theterminal, for example.

The other method is to previously notify a PUCCH resource to eachterminal from a base station (i.e., explicit signaling) (hereinafter,method 2). To put it differently, each terminal transmits responsesignals using the PUCCH resource previously notified by the base stationin method 2.

Each terminal can transmit response signals for downlink data usingmethod 1 or method 2 even when receiving downlink assignment controlinformation via an R-PDCCH.

However, method 1 requires that individual PUCCHs be associated with allR-CCEs that are distributed in the downlink frequency band, which causesa problem with the overhead of PUCCH resources. Moreover, as describedabove, an R-PDCCH is a resource region used temporarily when there is ashortage of PDCCH. For this reason, the R-PDCCH region is notnecessarily used for transmission of DCI always. Accordingly, there is apossibility that the majority of PUCCH resources associated with R-CCEsmay become useless in a certain time slot (i.e., certain subframe).

Meanwhile, method 2 requires that individual PUCCH resources bepreviously notified to all the terminals to which DCI may be transmittedusing an R-PDCCH.

Accordingly, method 2 also involves a problem with the overhead ofPUCCH.

In this respect, a description will be hereinafter provided regarding aterminal, a base station and a signal transmission control method thatmake it possible to reduce, as much as possible, the PUCCH required (tobe secured) for transmission of response signals for downlink data whena terminal receives downlink assignment control information via anR-PDCCH.

Embodiment 1

FIG. 9 is a main configuration diagram of base station 100 according toEmbodiment 1 of the claimed invention. In base station 100, a mappingsection 108 maps downlink control information (DCI) to one of a PDCCHtransmitted on one or a plurality of CCEs associated each with a PUCCH(uplink control channel) resource (i.e., first downlink control channel)and an R-PDCCH different from the PDCCH (i.e., second downlink controlchannel), and also maps data to a PDSCH (i.e., data channel).Accordingly, the DCI (downlink control information) is transmitted onone of the PDCCH and R-PDCCH, and the data is transmitted on a PDSCH.PUCCH extraction section 114 selects the resource used for transmissionof response signals for data in terminal 200, from a resource associatedwith a CCE, and a specific resource notified to terminal 200 accordingto whether the PDCCH (i.e., first downlink control channel) or R-PDCCH(i.e., second downlink control channel) is used to transmit the DCI(downlink control information) in mapping section 108, and uses theselected resource to extract the response signals. Accordingly, theresponse signals for the data are received.

FIG. 10 is a main configuration diagram of terminal 200 according toEmbodiment 1 of the claimed invention. In terminal 200, extractionsection 204 extracts the DCI (downlink control information) using thePDCCH (i.e., first downlink control channel) transmitted on one or aplurality of CCEs associated with a PUCCH (i.e., uplink control channel)resource or the R-PDCCH (i.e., second downlink control channel)different from the PDCCH, and also extracts the data using the PDSCH(i.e., data channel). Accordingly, the DCI is received on one of thePDCCH and R-PDCCH, and the data is received on the PDSCH. Responsesignal generating section 212 generates response signals for the data onthe basis of the presence or absence of error in the data. Controlsection 208 controls transmission of the response signals using a PUCCH(i.e., uplink control channel). In this case, control section 208controls the transmission of response signals by selecting a PUCCH(i.e., uplink control channel) resource used for the transmission ofresponse signals, from the resource associated with a CCE and thespecific resource notified from base station 100, according to whetherthe DCI (downlink control information) is received on the PDCCH (i.e.,first downlink control channel) or R-PDCCH (i.e., second downlinkcontrol channel).

(Configuration of Base Station)

FIG. 11 is a block diagram of base station 100 according to Embodiment 1of the claimed invention. In FIG. 11, base station 100 includes controlsection 101, control information generating section 102, coding section103, modulation section 104, coding section 105, data transmissioncontrolling section 106, modulation section 107, mapping section 108,inverse fast Fourier transform (IFFT) section 109, CP adding section110, radio transmitting section 111, radio receiving section 112, CPremoving section 113, PUCCH extracting section 114, despreading section115, sequence controlling section 116, correlation processing section117, A/N determining section 118, bundled A/N despreading section 119,inverse discrete Fourier transform (IDFT) section 120, bundled A/Ndetermining section 121 and retransmission control signal generatingsection 122.

Control section 101 assigns a downlink resource for transmitting controlinformation (i.e., downlink control information assignment resource) anda downlink resource for transmitting downlink data (i.e., downlink dataassignment resource) for a resource assignment target terminal(hereinafter, referred to as “destination terminal” or simply“terminal”) 200. This resource assignment is performed in a downlinkcomponent carrier included in a component carrier group configured forresource assignment target terminal 200. In addition, the downlinkcontrol information assignment resource is selected from among theresources corresponding to downlink control channels (i.e., PDCCH orR-PDCCH) in each downlink component carrier. Moreover, the downlink dataassignment resource is selected from among the resources correspondingto downlink data channel (i.e., PDSCH) in each downlink componentcarrier. However, the resources corresponding to the PDSCH and R-PDCCHare partially or entirely overlap each other, so that base station 100can divert the resources not used for the R-PDCCH to PDSCH. In addition,when there are a plurality of resource assignment target terminals 200,control section 101 assigns different resources to resource assignmenttarget terminals 200, respectively.

The downlink control information assignment resources are equivalent toL1/L2 CCH described above. To put it more specifically, the downlinkcontrol information assignment resources are each formed of one or aplurality of CCEs (or R-CCEs, and may be referred to as “CCE” simply,without any distinction between CCE and R-CCE).

Control section 101 determines the coding rate used for transmittingcontrol information to resource assignment target terminal 200. The datasize of the control information varies depending on the coding rate.Thus, control section 101 assigns a downlink control informationassignment resource having the number of CCEs that allows the controlinformation having this data size to be mapped to the resource.

Control section 101 outputs information on the downlink data assignmentresource to control information generating section 102. Moreover,control section 101 outputs information on the coding rate to codingsection 103. In addition, control section 101 determines and output thecoding rate of transmission data (i.e., downlink data) to coding section105. Moreover, control section 101 outputs information on the downlinkdata assignment resource and downlink control information assignmentresource to mapping section 108. However, control section 101 controlsthe assignment in such a way that the downlink data and downlink controlinformation for the downlink data are mapped to the same downlinkcomponent carrier.

Control information generating section 102 generates and outputs controlinformation including the information on the downlink data assignmentresource to coding section 103. This control information is generatedfor each downlink component carrier. In addition, when there are aplurality of resource assignment target terminals 200, the controlinformation includes the terminal ID of each destination terminal 200 inorder to distinguish resource assignment target terminals 200 from oneanother. For example, the control information includes CRC bits maskedby the terminal ID of destination terminal 200. This control informationmay be referred to as “control information carrying downlink assignment”or “downlink control information (DCI).”

Coding section 103 encodes the control information using the coding ratereceived from control section 101 and outputs the coded controlinformation to modulation section 104.

Modulation section 104 modulates the coded control information andoutputs the resultant modulation signals to mapping section 108.

Coding section 105 uses the transmission data (i.e., downlink data) foreach destination terminal 200 and the coding rate information fromcontrol section 101 as input and encodes and outputs the transmissiondata to data transmission controlling section 106. However, when aplurality of downlink component carriers are assigned to destinationterminal 200, coding section 105 encodes each piece of transmission datato be transmitted on a corresponding one of the downlink componentcarriers and transmits the coded pieces of transmission data to datatransmission controlling section 106.

Data transmission controlling section 106 outputs the coded transmissiondata to modulation section 107 and also keeps the coded transmissiondata at the initial transmission. Data transmission controlling section106 keeps the coded transmission data for each destination terminal 200.In addition, data transmission controlling section 106 keeps thetransmission data for one destination terminal 200 for each downlinkcomponent carrier on which the transmission data is transmitted. Thus,it is possible to perform not only retransmission control for overalldata transmitted to destination terminal 200, but also retransmissioncontrol for data on each downlink component carrier.

Furthermore, upon reception of a NACK or DTX for downlink datatransmitted on a certain downlink component carrier from retransmissioncontrol signal generating section 122, data transmission controllingsection 106 outputs the data kept in the manner described above andcorresponding to this downlink component carrier to modulation section107. Upon reception of an ACK for the downlink data transmitted on acertain downlink component carrier from retransmission control signalgenerating section 122, data transmission controlling section 106deletes the data kept in the manner described above and corresponding tothis downlink component carrier.

Modulation section 107 modulates the coded transmission data receivedfrom data transmission controlling section 106 and outputs the resultantmodulation signals to mapping section 108.

Mapping section 108 maps the modulation signals of the controlinformation received from modulation section 104 to the resourceindicated by the downlink control information assignment resourcereceived from control section 101 and outputs the resultant modulationsignals to IFFT section 109. Mapping section 108 herein maps the controlinformation (DCI) received from modulation section 104 to one of a PDCCHand R-PDCCH.

Mapping section 108 maps the modulation signals of the transmission datareceived from modulation section 107 to the resource (i.e., PDSCH (i.e.,downlink data channel)) indicated by the downlink data assignmentresource received from control section 101 (i.e., information includedin the control information) and outputs the resultant modulation signalsto IFFT section 109.

The control information and transmission data mapped to a plurality ofsubcarriers in a plurality of downlink component carriers in mappingsection 108 is transformed into time-domain signals fromfrequency-domain signals in IFFT section 109, and CP adding section 110adds a CP to the time-domain signals to form OFDM signals. The OFDMsignals undergo transmission processing such as digital to analog (D/A)conversion, amplification and up-conversion and/or the like in radiotransmitting section 111 and are transmitted to terminal 200 via anantenna.

Radio receiving section 112 receives, via an antenna, the uplinkresponse signals or reference signals transmitted from terminal 200 andperforms reception processing such as down-conversion, A/D conversionand/or the like on the uplink response signals or reference signals.

CP removing section 113 removes the CP added to the uplink responsesignals or reference signals from the uplink response signals orreference signals that have undergone the reception processing.

PUCCH extracting section 114 extracts, from the PUCCH signals includedin the received signals, the signals in the PUCCH region correspondingto the bundled ACK/NACK resource previously notified to terminal 200.The bundled ACK/NACK resource herein refers to a resource used fortransmission of the bundled ACK/NACK signals and adopting the DFT-S-OFDMformat structure. To put it more specifically, PUCCH extracting section114 extracts the data part of the PUCCH region corresponding to thebundled ACK/NACK resource (i.e., SC-FDMA symbols on which the bundledACK/NACK resource is assigned) and the reference signal part of thePUCCH region (i.e., SC-FDMA symbols on which the reference signals fordemodulating the bundled ACK/NACK signals are assigned). PUCCHextracting section 114 outputs the extracted data part to bundled A/Ndespreading section 119 and outputs the reference signal part todespreading section 115-1.

In addition, PUCCH extracting section 114 extracts, from the PUCCHsignals included in the received signals, a plurality of PUCCH regionscorresponding to an A/N resource associated with a CCE that has beenoccupied by the PDCCH used for transmission of the downlink assignmentcontrol information (DCI), and corresponding to a plurality of A/Nresources previously notified to terminal 200. The A/N resource hereinrefers to the resource to be used for transmission of an A/N. To put itmore specifically, PUCCH extracting section 114 extracts the data partof the PUCCH region corresponding to the A/N resource (i.e., SC-FDMAsymbols on which the uplink control signals are assigned) and thereference signal part of the PUCCH region (i.e., SC-FDMA symbols onwhich the reference signals for demodulating the uplink control signalsare assigned). In the extraction processing, PUCCH extracting section114 selects the resource used for transmission of the response signals(i.e., resource on which the signals from terminal 200 are assigned),from a PUCCH resource associated with a CCE and a specific PUCCHresource previously notified to terminal 200, according to whether thecontrol information is mapped to the PDCCH or R-PDCCH in mapping section108, and extracts the response signals using the selected resource.PUCCH extracting section 114 outputs both of the extracted data part andreference signal part to despreading section 115-2. In this manner, theresponse signals are received on the resource selected from the PUCCHresource associated with the CCE and the specific PUCCH resourcepreviously notified to terminal 200.

Sequence controlling section 116 generates a base sequence that may beused for spreading each of the A/N reported from terminal 200, thereference signals for the A/N, and the reference signals for the bundledACK/NACK signals (i.e., length-12 ZAC sequence). In addition, sequencecontrolling section 116 identifies a correlation window corresponding toa resource on which the reference signals may be assigned (hereinafter,referred to as “reference signal resource”) in PUCCH resources that maybe used by terminal 200. Sequence control section 116 outputs theinformation indicating the correlation window corresponding to thereference signal resource on which the reference signals may be assignedin bundled ACK/NACK resources and the base sequence to correlationprocessing section 117-1. Sequence controlling section 116 outputs theinformation indicating the correlation window corresponding to thereference signal resource and the base sequence to correlationprocessing section 117-1. In addition, sequence controlling section 116outputs the information indicating the correlation window correspondingto the A/N resources on which an A/N and the reference signals for theA/N are assigned and the base sequence to correlation processing section117-2.

Despreading section 115-1 and correlation processing section 117-1perform processing on the reference signals extracted from the PUCCHregion corresponding to the bundled ACK/NACK resource.

To put it more specifically, despreading section 115-1 despreads thereference signal part using a Walsh sequence to be used insecondary-spreading for the reference signals of the bundled ACK/NACKresource by terminal 200 and outputs the despread signals to correlationprocessing section 117-1.

Correlation processing section 117-1 uses the information indicating thecorrelation window corresponding to the reference signal resource andthe base sequence and thereby finds a correlation value between thesignals received from despreading section 115-1 and the base sequencethat may be used in primary-spreading in terminal 200. Correlationprocessing section 117-1 outputs the correlation value to bundled A/Ndetermining section 121.

Despreading section 115-2 and correlation processing section 117-2perform processing on the reference signals and A/Ns extracted from theplurality of PUCCH regions corresponding to the plurality of A/Nresources.

To put it more specifically, despreading section 115-2 despreads thedata part and reference signal part using a Walsh sequence and a DFTsequence to be used in secondary-spreading for the data part andreference signal part of each of the A/N resources by terminal 200, andoutputs the despread signals to correlation processing section 117-2.

Correlation processing section 117-2 uses the information indicating thecorrelation window corresponding to each of the A/N resources and thebase sequence and thereby finds a correlation value between the signalsreceived from despreading section 115-2 and a base sequence that may beused in primary-spreading by terminal 200. Correlation processingsection 117-2 outputs each correlation value to A/N determining section118.

A/N determining section 118 determines, on the basis of the plurality ofcorrelation values received from correlation processing section 117-2,which of the A/N resources is used to transmit the signals from terminal200 or none of the A/N resources is used. When determining that thesignals are transmitted using one of the A/N resources from terminal200, A/N determining section 118 performs coherent detection using acomponent corresponding to the reference signals and a componentcorresponding to the A/N and outputs the result of coherent detection toretransmission control signal generating section 122. Meanwhile, whendetermining that terminal 200 uses none of the A/N resources, A/Ndetermining section 118 outputs the determination result indicating thatnone of the A/N resources is used to retransmission control signalgenerating section 122.

Bundled A/N despreading section 119 despreads, using a DFT sequence, thebundled ACK/NACK signals corresponding to the data part of the bundledACK/NACK resource received from PUCCH extracting section 114 and outputsthe despread signals to IDFT section 120.

IDFT section 120 transforms the bundled ACK/NACK signals in thefrequency-domain received from bundled A/N despreading section 119 intotime-domain signals by IDFT processing and outputs the bundled ACK/NACKsignals in the time-domain to bundled A/N determining section 121.

Bundled A/N determining section 121 demodulates the bundled ACK/NACKsignals corresponding to the data part of the bundled ACK/NACK resourcereceived from IDFT section 120, using the reference signal informationon the bundled ACK/NACK signals that is received from correlationprocessing section 117-1. In addition, bundled A/N determination section121 decodes the demodulated bundled ACK/NACK signals and outputs theresult of decoding to retransmission control signal generating section122 as the bundled A/N information. However, when the correlation valuereceived from correlation processing section 117-1 is smaller than athreshold, and bundled A/N determining section 121 thus determines thatterminal 200 does not use any bundled A/N resource to transmit thesignals, bundled A/N determining section 121 outputs the result ofdetermination to retransmission control signal generating section 122.

Retransmission control signal generating section 122 determines whetheror not to retransmit the data transmitted on the downlink componentcarrier (i.e., downlink data) on the basis of the information receivedfrom bundled A/N determining section 121 and the information receivedfrom A/N determining section 118 and generates retransmission controlsignals based on the result of determination. To put it morespecifically, when determining that downlink data transmitted on acertain downlink component carrier needs to be retransmitted,retransmission control signal generating section 122 generatesretransmission control signals indicating a retransmission command forthe downlink data and outputs the retransmission control signals to datatransmission controlling section 106. In addition, when determining thatthe downlink data transmitted on a certain downlink component carrierdoes not need to be retransmitted, retransmission control signalgenerating section 122 generates retransmission control signalsindicating not to retransmit the downlink data transmitted on thedownlink component carrier and outputs the retransmission controlsignals to data transmission controlling section 106.

It should be noted that, the retransmission control in A/N determiningsection 118, bundled A/N determining section 121 and retransmissioncontrol signal generating section 122 will be described in detail,hereinafter.

(Configuration of Terminal)

FIG. 12 is a block diagram illustrating a configuration of terminal 200according to Embodiment 1. In FIG. 12, terminal 200 includes radioreceiving section 201, CP removing section 202, fast Fourier transform(FFT) section 203, extraction section 204, demodulation section 205,decoding section 206, determination section 207, control section 208,demodulation section 209, decoding section 210, CRC section 211,response signal generating section 212, coding and modulation section213, primary-spreading sections 214-1 and 214-2, secondary-spreadingsections 215-1 and 215-2, DFT section 216, spreading section 217, IFFTsections 218-1, 218-2 and 218-3, CP adding sections 219-1, 219-2 and219-3, time-multiplexing section 220, selection section 221 and radiotransmitting section 222.

Radio receiving section 201 receives, via an antenna, OFDM signalstransmitted from base station 100 and performs reception processing suchas down-conversion, A/D conversion and/or the like on the received OFDMsignals. It should be noted that, the received OFDM signals includePDSCH signals assigned to a resource in a PDSCH (i.e., downlink data),R-PDCCH signals assigned to a resource in an R-PDCCH or PDCCH signalsassigned to a resource in a PDCCH. Hereinafter, the R-PDCCH signals andPDCCH signals may be referred to as “PDCCH signals” or “downlink controlchannel signals” simply without any distinction between R-PDCCH signalsand PDCCH signals.

CP removing section 202 removes a CP that has been added to the OFDMsignals from the OFDM signals that have undergone the receptionprocessing.

FFT section 203 transforms the received OFDM signals intofrequency-domain signals by FFT processing and outputs the resultantreceived signals to extraction section 204.

Extraction section 204 extracts, from the received signals to bereceived from FFT section 203, downlink control channel signals (i.e.,PDCCH signals or R-PDCCH signals) in accordance with coding rateinformation to be received. To put it more specifically, the number ofCCEs (or R-CCEs) forming a downlink control information assignmentresource varies depending on the coding rate. Thus, extraction section204 uses the number of CCEs that corresponds to the coding rate as unitsof extraction processing, and extracts downlink control channel signals.In addition, the downlink control channel signals are extracted for eachdownlink component carrier. The extracted downlink control channelsignals are outputted to demodulation section 205.

Extraction section 204 extracts downlink data (i.e., downlink datachannel signals (i.e., PDSCH signals)) from the received signals on thebasis of information on the downlink data assignment resource intendedfor terminal 200 to be received from determination section 207 to bedescribed, hereinafter, and outputs the downlink data to demodulationsection 209. As described above, extraction section 204 receives thedownlink assignment control information (i.e., DCI) mapped to one of thePDCCH and R-PDCCH and receives the downlink data on the PDSCH.

Demodulation section 205 demodulates the downlink control channelsignals received from extraction section 204 and outputs the obtainedresult of demodulation to decoding section 206.

Decoding section 206 decodes the result of demodulation received fromdemodulation section 205 in accordance with the received coding rateinformation and outputs the obtained result of decoding to determinationsection 207.

Determination section 207 performs blind-determination (i.e.,monitoring) to find out whether or not the control information includedin the result of decoding received from decoding section 206 is thecontrol information intended for terminal 200. This determination ismade in units of decoding results corresponding to the units ofextraction processing. For example, determination section 207 demasksthe CRC bits by the terminal ID of terminal 200 and determines that thecontrol information resulted in CRC=OK (no error) as the controlinformation intended for terminal 200. Determination section 207 outputsinformation on the downlink data assignment resource intended forterminal 200, which is included in the control information intended forterminal 200, to extraction section 204.

In addition, when detecting the control information (i.e., downlinkassignment control information) intended for terminal 200, determinationsection 207 informs control section 208 that ACK/NACK signals will begenerated (or are present). Moreover, when detecting the controlinformation intended for terminal 200 from PDCCH signals, determinationsection 207 outputs information on a CCE that has been occupied by thePDCCH to control section 208.

Control section 208 identifies the A/N resource associated with the CCEon the basis of the information on the CCE received from determinationsection 207. Control section 208 outputs, to primary-spreading section214-1, a base sequence and a cyclic shift value corresponding to the A/Nresource associated with the CCE or the A/N resource previously notifiedby base station 100, and also outputs a Walsh sequence and a DFTsequence corresponding to the A/N resource to secondary-spreadingsection 215-1. In addition, control section 208 outputs the frequencyresource information on the A/N resource to IFFT section 218-1.

When determining to transmit bundled ACK/NACK signals using a bundledACK/NACK resource, control section 208 outputs the base sequence andcyclic shift value corresponding to the reference signal part (i.e.,reference signal resource) of the bundled ACK/NACK resource previouslynotified by base station 100 to primary-despreading section 214-2 andoutputs a Walsh sequence to secondary-despreading section 215-2. Inaddition, control section 208 outputs the frequency resource informationon the bundled ACK/NACK resource to IFFT section 218-2.

Control section 208 outputs a DFT sequence used for spreading the datapart of the bundled ACK/NACK resource to spreading section 217 andoutputs the frequency resource information on the bundled ACK/NACKresource to IFFT section 218-3.

Control section 208 selects the bundled ACK/NACK resource or the A/Nresource and instructs selection section 221 to output the selectedresource to radio transmitting section 222. During this process, controlsection 208 controls the transmission of the response signals byselecting the resource used for transmission of the response signals,from the PUCCH resource associated with the CCE and the specific PUCCHresource previously notified by base station 100, according to whetherthe downlink assignment control information (DCI) is mapped to the PDCCHor R-PDCCH. Control section 208 instructs response signal generatingsection 212 to generate the bundled ACK/NACK signals or the ACK/NACKsignals in accordance with the selected resource. The method ofdetermining the A/N resource as well as the method of controlling thebundled ACK/NACK resource in control section 208 will be described indetail, hereinafter.

Demodulation section 209 demodulates the downlink data received fromextraction section 204 and outputs the demodulated downlink data todecoding section 210.

Decoding section 210 decodes the downlink data received fromdemodulation section 209 and outputs the decoded downlink data to CRCsection 211.

CRC section 211 performs error detection on the decoded downlink datareceived from decoding section 210, for each downlink component carrierusing CRC and outputs an ACK when CRC=OK (no error) or outputs a NACKwhen CRC=Not OK (error) to response signal generating section 212.Moreover, CRC section 211 outputs the decoded downlink data as thereceived data when CRC=OK (no error).

Response signal generating section 212 generates response signals on thebasis of the reception condition of downlink data (i.e., result of errordetection on downlink data) on each downlink component carrier receivedfrom CRC section 211. To put it more specifically, when instructed togenerate the bundled ACK/NACK signals from control section 208, responsesignal generating section 212 generates the bundled ACK/NACK signalsincluding the results of error detection for the respective componentcarriers as individual pieces of data. Meanwhile, when instructed togenerate ACK/NACK signals from control section 208, response signalgenerating section 212 generates ACK/NACK signals of one symbol.Response signal generating section 212 outputs the generated responsesignals to coding and modulation section 213.

Upon reception of the bundled ACK/NACK signals, coding and modulationsection 213 encodes and modulates the received bundled ACK/NACK signalsto generate the modulation signals of 12 symbols and outputs themodulation signals to DFT section 216. In addition, upon reception ofthe ACK/NACK signals of one symbol, coding and modulation section 213modulates the ACK/NACK signals and outputs the modulation signals toprimary-spreading section 214-1.

DFT section 216 performs DFT processing on 12 time-series sets ofreceived bundled ACK/NACK signals to obtain 12 signal components in thefrequency-domain. DFT section 216 outputs the 12 signal components tospreading section 217.

Spreading section 217 spreads the 12 signal components received from DFTsection 216 using a DFT sequence indicated by control section 208 andoutputs the spread signal components to IFFT section 218-3.

Primary-spreading sections 214-1 and 214-2 corresponding to the A/Nresource and the reference signal resource of bundled ACK/NACK resourcespread ACK/NACK signals or reference signals using a base sequencecorresponding to the resource in accordance with an instruction fromcontrol section 208 and outputs the spread signals tosecondary-spreading sections 215-1 and 215-2.

Secondary-spreading sections 215-1 and 215-2 spread the receivedprimary-spread signals using a Walsh sequence or a DFT sequence inaccordance with an instruction from control section 208 and outputs thespread signals to IFFT sections 218-1 and 218-2.

IFFT sections 218-1, 218-2 and 218-3 perform IFFT processing on thereceived signals in association with the frequency positions where thesignals are to be placed, in accordance with an instruction from controlsection 208. Accordingly, the signals inputted to IFFT sections 218-1,218-2 and 218-3 (i.e., ACK/NACK signals, the reference signals of A/Nresource, the reference signals of bundled ACK/NACK resource and bundledACK/NACK signals) are transformed into time-domain signals.

CP adding sections 219-1, 219-2 and 219-3 add the same signals as thelast part of the signals obtained by IFFT processing to the beginning ofthe signals as a CP.

Time-multiplexing section 220 time-multiplexes the bundled ACK/NACKsignals received from CP adding section 219-3 (i.e., signals transmittedusing the data part of the bundled ACK/NACK resource) and the referencesignals of the bundled ACK/NACK resource to be received from CP addingsection 219-2 on the bundled ACK/NACK resource and outputs themultiplexed signals to selection section 221.

Selection section 221 selects one of the bundled ACK/NACK resourcereceived from time-multiplexing section 220 and the A/N resourcereceived from CP adding section 219-1 and outputs the signals assignedto the selected resource to radio transmitting section 222.

Radio transmitting section 222 performs transmission processing such asD/A conversion, amplification and up-conversion and/or the like on thesignals received from selection section 221 and transmits the resultantsignals to base station 100 via an antenna.

(Operations of Base Station 100 and Terminal 200)

A description will be provided regarding operations of base station 100and terminal 200 each configured in the manner described above.

In the following description, an assumption is made that whether to useonly a PDCCH for transmission of downlink assignment control informationor to use a PDCCH in combination with an R-PDCCH is already configuredfor each of a plurality of terminals 200 and notified to each terminal200 as the result of configuration. However, even when configuringterminal 200 to use an R-PDCCH, base station 100 selectively uses aPDCCH and R-PDCCH depending on circumstances. For example, when thereare only few terminals 200 to which control information is to betransmitted in a certain subframe, base station 100 transmits controlinformation to all terminals 200 (including a terminal configured to usean R-PDCCH) using a PDCCH. Meanwhile, when there are many terminals 200to which control information is to be transmitted in a certain subframe,for example, base station 100 transmits control information to some ofterminals 200 (i.e., terminals 200 configured to use an R-PDCCH) usingan R-PDCCH.

Four examples of how A/N resources used for transmission of responsesignals are controlled (hereinafter, referred to as control examples 1to 4) will be described, hereinafter.

Control Example 1 No Carrier Aggregation

Base station 100 previously and explicitly notifies one specific A/Nresource to terminal 200 using RRC signaling and/or the like (explicitsignaling), for example, together with the result of configuration of adownlink control channel, when configuring an R-PDCCH for terminal 200as a downlink control channel used for transmission of downlinkassignment control information (i.e., DCI). For example, base station100 explicitly notifies a specific PUCCH resource in PUCCH region 2(PUCCH 2) as the A/N resource to terminal 200 configured to use anR-PDCCH in FIGS. 13A and 13B.

In FIGS. 13A and 13B, CCEs included in the PDCCH are associated in aone-to-one correspondence with PUCCH resources (i.e., A/N resources) inPUCCH region 1 (PUCCH 1) (implicit signaling).

Base station 100 maps the downlink assignment control information (i.e.,DCI) to the PDCCH or R-PDCCH and transmits the downlink assignmentcontrol information (i.e., DCI) to terminal 200.

When configured to use a PDDCH and R-PDCCH by base station 100, terminal200 detects the downlink assignment control information (i.e., DCI)intended for terminal 200, by performing blind-decoding (monitoring) inboth of the PDCCH region and R-PDCCH region. Terminal 200 (i.e.,extraction section 204) extracts downlink data (DL data) on the basis ofthe downlink assignment control information mapped to one of the PDCCHand R-PDCCH.

Subsequently, terminal 200 detects the presence or absence of an errorin receiving the downlink data (DL data) assigned using the downlinkassignment control information (i.e., DCI) intended for terminal 200 andtransmits ACK/NACK signals using a PUCCH on an uplink component carrieron the basis of the result of error detection. During this processing,terminal 200 selects the A/N resource used for transmission of theACK/NACK signals, from the PUCCH resource associated with the CCE andthe specific A/N resource previously notified by base station 100,according to whether the downlink assignment control information (i.e.,DCI) intended for terminal 200 is mapped to the PDCCH or R-PDCCH (i.e.,according to whether the downlink assignment control information isreceived on the PDCCH or R-PDCCH).

To put it more specifically, upon reception of the downlink assignmentcontrol information (i.e., DCI) intended for terminal 200 on the PDCCH,terminal 200 (i.e., control section 208) selects the PUCCH resourceassociated in a one-to-one correspondence with the CCE to which thedownlink assignment control information is mapped (i.e., CCE on whichthe PDCCH has been transmitted or CCE that has been occupied by thePDCCH used for transmission of the downlink assignment controlinformation) (i.e., PUCCH resource in PUCCH 1), as the A/N resource usedfor transmission of ACK/NACK signals as illustrated in FIG. 13A.Terminal 200 transmits the ACK/NACK signals using the selected A/Nresource.

On the other hand, upon reception of the downlink assignment controlinformation (i.e., DCI) intended for terminal 200 on the R-PDCCH,terminal 200 (i.e., control section 208) selects the specific A/Nresource previously and explicitly notified by base station 100 (i.e.,PUCCH resource in PUCCH 2, as the A/N resource used for transmission ofACK/NACK signals as illustrated in FIG. 13B. Terminal 200 transmits theACK/NACK signals using the selected A/N resource.

In addition, base station 100 selects the PUCCH resource used fortransmission of the ACK/NACK signals from terminal 200 in accordancewith the downlink control channel (i.e., PDCCH or R-PDCCH) to which thedownlink assignment control information intended for each terminal 200is mapped and extracts the signals included in the selected PUCCHresource.

As described above, base station 100 explicitly notifies the A/Nresource to terminal 200. Thus, base station 100 does not have toassociate the PUCCH resources with all the R-CCEs in a one-to-onecorrespondence unlike method 1 described above. Accordingly, it ispossible to minimize an increase in the number of A/N resources to besecured for transmission of ACK/NACK signals for the downlink dataassigned using the downlink assignment control information transmittedon an R-PDCCH, i.e., to minimize an increase in the overhead of PUCCHresources.

Meanwhile, although base station 100 previously and explicitly notifiesone A/N resource to terminal 200, it is not true that terminal 200always uses the A/N resource for transmission of ACK/NACK signals. Toput it more specifically, upon reception of downlink assignment controlinformation on a PDCCH, terminal 200 preferentially uses the PUCCHresource associated with the CCE that has been occupied by the PDCCHused for transmission of the downlink assignment control information.

Thus, even if base station 100 explicitly notifies the same A/N resource(i.e., A/N resource previously notified as illustrated in FIGS. 13A andB) to a plurality of terminals 200, the limitation on a scheduler ofbase station 100 is only “not to assign downlink assignment controlinformation for the plurality of terminals 200 to which the same A/Nresource has been notified, to the R-PDCCH region in the same subframe.”For example, base station 100 may transmit, using an R-PDCCH, only thedownlink assignment control information intended for one terminal 200among the plurality of terminals 200 to which the same A/N resource hasbeen notified, and transmit the downlink assignment control informationintended for the other remaining terminals 200 using a PDCCH.Accordingly, only one terminal 200 transmits the response signals usingthe A/N resource that has been notified to the plurality of terminals200. To put it differently, base station 100 can control ACK/NACKsignals from terminals 200 so as to avoid a collision between ACK/NACKsignals from terminals 200 while allowing a plurality of terminals 200to share a single A/N resource through the extremely simple schedulingdescribed above.

Accordingly, base station 100 can configure a common A/N resource forterminals 200, thereby eliminating the need for configuring individualA/N resources for respective terminals 200 unlike method 2 describedabove, and thus minimizing an increase in the overhead of PUCCHresources.

Accordingly, in control example 1, a plurality of terminals 200 canshare the same A/N resource while preferentially using the PUCCHresource previously associated with the CCE that has been occupied bythe PDCCH. Thus, the use efficiency of PUCCH resources can be improvedwith almost no additional limitations on a scheduler of base station100. In other words, terminal 200 can efficiently transmit ACK/NACKsignals even when receiving downlink assignment control information onan R-PDCCH.

Control Example 2 With Carrier Aggregation and Channel Selection

In control example 2, two downlink component carriers and one uplinkcomponent carrier are configured for terminals 200 as illustrated inFIGS. 14A and B. To put it more specifically, base station 100 andterminals 200 communicate with each other using two downlink componentcarriers and one uplink component carrier, i.e., using asymmetriccarrier aggregation.

In addition, channel selection is employed as a method of transmittingresponse signals (i.e., ACK/NACK signals) in terminals 200. In FIGS. 14Aand B, two results of error detection on pieces of downlink datatransmitted using the two downlink component carriers, respectively(i.e., four combinations), need to be fed back. Accordingly, channelselection requires two A/N resources (i.e., PUCCH resources).

In addition, as illustrated in FIGS. 14A and B, one of the two downlinkcomponent carriers configured for terminal 200 is paired with one uplinkcomponent carrier to be used for transmission of response signals. Thedownlink component carrier paired with the uplink component carrier tobe used for transmission of response signals is called a primarycomponent carrier (PCC) or a primary cell (Pcell). For example, PCC (orPcell) is the downlink component carrier used to transmit broadcastinformation about the uplink component carrier on which response signalsto be transmitted (e.g., system information block type 2 (SIB 2)). Inaddition, the CCEs included in the PDCCH region in PCC (or Pcell) areassociated with PUCCH resources in the uplink component carrier (i.e.,PUCCH resources in PUCCH 1 in FIGS. 14A and B) in a one-to-onecorrespondence (implicit signaling).

In this case, when previously configuring, for terminal 200, an R-PDCCHas a downlink control channel used for transmission of downlinkassignment control information (i.e., DCI) in Pcell, base station 100explicitly notifies two specific A/N resources together with the resultof configuration of the downlink control channel, for example, using RRCsignaling (explicit signaling). In FIGS. 14A and B, base station 100explicitly notifies two specific PUCCH resources in PUCCH region 2(PUCCH 2) as A/N resource 1 and A/N resource 2 to terminals 200 forwhich the R-PDCCH is configured, for example.

Base station 100 maps downlink assignment control information (i.e.,DCI) to the PDCCH or R-PDCCH in Pcell and transmits the downlinkassignment control information (i.e., DCI) to terminals 200. Inaddition, base station 100 maps downlink assignment control information(i.e., DCI) to the PDCCH on the downlink component carrier other thanPcell and transmits the downlink assignment control information (i.e.,DCI) to terminals 200.

Each terminal 200 detects the downlink assignment control information(i.e., DCI) intended for terminal 200 by performing blind-decoding(i.e., monitoring) in both of the PDCCH region and R-PDCCH region atleast in Pcell. Terminal 200 (i.e., extraction section 204) extractsdownlink data (DL data) on the basis of the downlink assignment controlinformation mapped to one of the PDCCH and R-PDCCH. Accordingly,terminal 200 receives downlink data on each of the plurality of downlinkcomponent carriers.

Subsequently, terminal 200 (i.e., CRC section 211) detects the presenceor absence of an error in receiving the downlink data (DL data) assignedusing the downlink assignment control information (i.e., DCI) intendedfor terminal 200 in each of the downlink component carriers. Moreover,response signal generating section 212 generates ACK/NACK signals inaccordance with the pattern of the results of error detection (presenceor absence of reception errors) on the pieces of downlink data in therespective downlink component carriers. Terminal 200 transmits theACK/NACK signals using the PUCCH on the uplink component carrier. Forthis transmission, terminal 200 selects the A/N resource used fortransmission of the ACK/NACK signals, from the PUCCH resource associatedwith the CCE and the specific A/N resources previously notified by basestation 100, according to whether the downlink assignment controlinformation (i.e., DCI) intended for terminal 200 is mapped to the PDCCHor R-PDCCH in Pcell.

To put it more specifically, as illustrated in FIG. 14A, upon receptionof the downlink assignment control information intended for terminal 200on the PDCCH in Pcell of the two downlink component carriers, terminal200 (i.e., control section 208) performs the channel selection operationusing two A/N resources including the PUCCH resource associated in aone-to-one correspondence with the CCE (i.e., PUCCH resource in PUCCH 1)to which the downlink assignment control information is mapped (i.e.,CCE used for transmission of the PDCCH) and A/N resource 1 previouslyand explicitly notified by base station 100. To put it differently,terminal 200 selects which phase point of which one of the two A/Nresources is used to transmit the ACK/NACK signals on the basis of thereception conditions (pattern of the presence or absence of receptionerrors) of the pieces of downlink data received on the respective twodownlink component carriers in FIG. 14A. Terminal 200 transmits theACK/NACK signals using the selected A/N resource and phase point.

Meanwhile, as illustrated in FIG. 14B, upon reception of the downlinkassignment control information intended for terminal 200 on the R-PDCCHin Pcell of the two downlink component carriers, terminal 200 (i.e.,control section 208) performs the channel selection operation using thetwo A/N resources previously and explicitly notified by base station 100(i.e., A/N resource 1 and A/N resource 2).

As described above, base station 100 explicitly notifies the A/Nresources (e.g., A/N resources 1 and 2 in FIGS. 14A and B) to terminal200, so that base station 100 does not have to associate the PUCCHresources to all the R-CCEs in a one-to-one correspondence unlike method1 described above. Thus, it is possible to minimize an increase in thenumber of A/N resources to be secured for transmission of ACK/NACKsignals for the downlink data assigned by the downlink assignmentcontrol information transmitted via an R-PDCCH, i.e., to minimize anincrease in the overhead of PUCCH resources.

Moreover, when terminal 200 receives downlink assignment controlinformation via the PDCCH in Pcell although A/N resources are previouslyand explicitly notified to terminal 200 by base station 100, terminal200 preferentially uses the PUCCH resource associated with the CCE thathas been occupied by the PDCCH in Pcell used for transmission of thedownlink assignment control information as in the case of controlexample 1. Thus, base station 100 can control ACK/NACK signals fromterminals 200 so as to avoid a collision between ACK/NACK signals fromterminals 200 while allowing a plurality of terminals 200 to share A/Nresources through the extremely simple scheduling as in the case ofcontrol example 1, thereby minimizing an increase in the overhead ofPUCCH resources.

Thus, in control example 2, a plurality of terminals 200 can share thesame A/N resources while preferentially using the PUCCH resourcepreviously associated with the CCE that has been occupied by the PDCCHin Pcell. Thus, the use efficiency of PUCCH resources can be improvedwith almost no additional limitations on a scheduler of base station100. To put it differently, even when terminal 200 receives downlinkassignment control information on an R-PDCCH in a case where channelselection is applied, terminal 200 can efficiently transmit ACK/NACKsignals.

In FIGS. 14A and B, the case where terminal 200 monitors the R-PDCCHregion only in Pcell has been described. However, the operation ofcontrol example 2 described above can be also applied to a case whereterminal 200 monitors an R-PDCCH region in a downlink component carrierother than Pcell, i.e., a case where an R-PDCCH is configured in adownlink component carrier other than Pcell.

Moreover, although the case where two downlink component carriers areconfigured for terminal 200 has been described in FIGS. 14A and B, thenumber of downlink component carriers configured for terminal 200 can bethree or more. When the number of downlink component carriers configuredfor terminal 200 is three or more, the number of combinations of resultsof error detection on the respective downlink component carriers (i.e.,patterns of the presence or absence of reception errors) increases, sothat the number of resources required for channel selection (e.g., tworesources when the number of downlink component carriers is two)increases as well. In this case, base station 100 may determine thenumber of A/N resources to be previously and explicitly notified toterminal 200 on the basis of the number of downlink component carriersconfigured for terminal 200.

In addition, although the case where base station 100 configures both ofcarrier aggregation and channel selection for terminal 200 has beendescribed in control example 2, there may be a situation where basestation 100 performs downlink data assignment without using carrieraggregation (i.e., non-carrier aggregation assignment) for terminal 200depending on circumstances even when such a configuration is employed.When base station 100 performs downlink data assignment without usingcarrier aggregation for terminal 200 in a certain subframe, terminal 200performs, in the subframe, the operation illustrated in FIG. 13. In thiscase, however, the A/N resource in FIG. 13 and the A/N resource 1 (orA/N resource 2) in FIG. 14 can be configured as the same resource.Accordingly, there is no need for base station 100 to report anadditional A/N resource to terminal 200 even when base station 100adaptively selects between communications using carrier aggregation andcommunications without using carrier aggregation. As a result, theoverhead can be reduced.

Control Example 3 With Carrier Aggregation and DFT-S-OFDM Format

In control example 3, two downlink component carriers and one uplinkcomponent carrier are configured for terminals 200 as illustrated inFIGS. 15A to D.

In addition, the DFT-S-OFDM format is applied as a method oftransmitting response signals in terminals 200.

Moreover, one of the two downlink component carriers configured forterminals 200 is Pcell (or PCC) and the CCEs included in the PDCCHregion in Pcell are associated in a one-to-one correspondence with PUCCHresources in the uplink component carrier (i.e., PUCCH resources inPUCCH 1 in FIGS. 15A to D) (implicit signaling) as illustrated in FIGS.15A to D.

In control example 3, when previously configuring an R-PDCCH as thedownlink control channel used for transmission of downlink assignmentcontrol information (i.e., DCI) in Pcell, or configuring carrieraggregation for terminals 200, base station 100 explicitly notifies onebundled A/N resource (i.e., resource having the DFT-S-OFDM format(sometimes called a large ACK/NACK resource) together with the result ofconfiguration, for example, using RRC signaling and/or the like(explicit signaling). For example, base station 100 explicitly notifiesspecific PUCCH resources in PUCCH region 2 (PUCCH 2) to terminals 200 asa bundled A/N resource in FIGS. 15A to D.

In addition, base station 100 maps downlink assignment controlinformation (i.e., DCI) to the PDCCH or R-PDCCH in Pcell and transmitsthe downlink assignment control information (i.e., DCI) to terminals200. Moreover, base station 100 maps downlink assignment controlinformation (i.e., DCI) to the PDCCH in the downlink component carrierother than Pcell and transmits the downlink assignment controlinformation (i.e., DCI) to terminals 200.

Each terminal 200 detects the downlink assignment control information(i.e., DCI) intended for terminal 200 by performing blind-decoding(i.e., monitoring) in both of the PDCCH region and R-PDCCH region atleast in Pcell. Terminal 200 (i.e., extraction section 204) extractsdownlink data (DL data) on the basis of the downlink assignment controlinformation mapped to one of the PDCCH region and R-PDCCH. In thismanner, terminal 200 receives the downlink assignment controlinformation and downlink data for each downlink component carrier in atleast one of the plurality of downlink component carriers.

Subsequently, terminal 200 (i.e., CRC section 211) detects the presenceor absence of an error in receiving downlink data (DL data) assignedusing the downlink assignment control information (i.e., DCI) intendedfor terminal 200 in each of the downlink component carriers. Inaddition, response signal generating section 212 generates responsesignals on the basis of the results of error detection on the pieces ofdownlink data on the respective downlink component carriers (i.e.,presence or absence of errors), i.e., bundled ACK/NACK signals (i.e.,response signals including the presence or absence of reception errorsin the respective pieces of downlink data) or ACK/NACK signals. Terminal200 transmits the response signals (i.e., ACK/NACK signals or bundledACK/NACK signals) using a PUCCH in the uplink component carrier. Forthis transmission, terminal 200 selects the A/N resource used fortransmission of the response signals, from the PUCCH resource associatedwith the CCE and the specific bundled A/N resource previously notifiedby base station 100, according to whether the downlink assignmentcontrol information (i.e., DCI) intended for terminal 200 is mapped tothe PDCCH or R-PDCCH in Pcell.

To put it more specifically, as illustrated in FIG. 15A, when receivingthe downlink assignment control information intended for terminal 200 onthe PDCCH in Pcell but receiving no downlink assignment controlinformation on the other downlink component carrier (i.e., secondarycomponent carrier (SCC)) or secondary cell (Scell)) among the pluralityof downlink component carriers, terminal 200 selects the PUCCH resource(PUCCH resource in PUCCH 1) associated in a one-to-one correspondencewith the CCE to which the downlink assignment control information ismapped (i.e., CCE used for transmission of the PDCCH). Terminal 200transmits the response signals (i.e., ACK/NACK signals) for the downlinkdata (DL data) received in Pcell using the selected PUCCH resource.

In addition, when receiving the downlink assignment control informationintended for terminal 200 on the R-PDCCH in Pcell but receiving nodownlink assignment control information on the other downlink componentcarrier, terminal 200 (i.e., control section 208) selects the bundledA/N resource previously and explicitly notified by base station 100 asillustrated in FIG. 15B. Terminal 200 transmits the response signals(i.e., ACK/NACK signals) for the downlink data (DL data) received inPcell using the selected bundled A/N resource.

In addition, when receiving the downlink assignment control informationintended for terminal 200 on the PDCCH in Pcell and also receiving thedownlink assignment control information on the other downlink componentcarrier, terminal 200 (i.e., control section 208) selects the bundledA/N resource previously and explicitly notified by base station 100 asillustrated in FIG. 15C. Terminal 200 transmits the bundled A/N signalsobtained by jointly encoding (i.e., joint coding) the response signalsfor the pieces of downlink data (DL data) received respectively in Pcelland in the other downlink component carrier using the selected bundledA/N resources.

In addition, when receiving the downlink assignment control informationintended for terminal 200 on the R-PDCCH in Pcell and also receiving thedownlink assignment control information on the other downlink componentcarrier, terminal 200 (i.e., control section 208) selects the bundledA/N resource previously and explicitly notified by base station 100 asillustrated in FIG. 15D. Terminal 200 transmits the bundled A/N signalsobtained by jointly encoding (i.e., joint coding) the response signalsfor the pieces of downlink data (DL data) received respectively in Pcelland in the other downlink component carrier using the selected bundledA/N resource.

In other words, when receiving downlink assignment control informationin Pcell and also receiving downlink assignment control information inthe other downlink component carrier among the plurality of downlinkcomponent carriers (i.e., carrier aggregation assignment in FIGS. 15Cand 15D), terminal 200 uses the bundled A/N resource previously andexplicitly notified by base station 100, regardless of the downlinkcontrol channel used for transmission of the downlink assignment controlinformation in Pcell (i.e., PDCCH and R-PDCCH).

As described above, base station 100 previously and explicitly notifiesa bundled A/N resource to terminal 200, so that base station 100 doesnot have to associate the PUCCH resources with all the R-CCEs in aone-to-one correspondence unlike method 1 described above. Thus, it ispossible to minimize an increase in the number of A/N resources to besecured for transmission of ACK/NACK signals for the downlink dataassigned by the downlink assignment control information transmitted onan R-PDCCH, i.e., to minimize an increase in the overhead of PUCCHresources.

Moreover, as in control example 1, although base station 100 previouslyand explicitly notifies one bundled A/N resource to terminal 200, it isnot true that terminal 200 always uses the bundled A/N resource fortransmission of ACK/NACK signals. To put it more specifically, whenreceiving downlink assignment control information on the PDCCH in Pcellbut receiving no downlink assignment control information in the otherdownlink component carrier, terminal 200 preferentially uses the PUCCHresource associated with the CCE that has been occupied by the PDCCHused for transmission of the downlink assignment control information inPcell. In other words, the bundled A/N resource (i.e., resource havingthe DFT-S-OFDM format) is used in terminal 200 only when necessary.Thus, a plurality of terminals 200 can share the same bundled A/Nresource. Thus, base station 100 can control response signals fromterminals 200 so as to avoid a collision between the response signalsfrom terminals 200 while allowing a plurality of terminals 200 to sharethe same bundled A/N resource through the extremely simple scheduling asin the case of control example 1, thereby minimizing an increase in theoverhead of PUCCH resources.

Accordingly, in control example 3, a plurality of terminals 200 canshare the same bundled A/N resource while preferentially using the PUCCHresource previously associated with the CCE that has been occupied bythe PDCCH in Pcell. Thus, the use efficiency of PUCCH resources can beimproved with almost no additional limitations on a scheduler of basestation 100. To put it differently, terminal 200 can efficientlytransmit response signals even when receiving downlink assignmentcontrol information on an R-PDCCH in a case where the DFT-S-OFDM formatis adopted.

In FIGS. 15A to D, the case where terminal 200 monitors an R-PDCCHregion only in Pcell has been described. However, the operation ofcontrol example 3 can be applied to a case where terminal 200 monitorsan R-PDCCH in a downlink component carrier other than Pcell, i.e., acase where an R-PDCCH is configured in a downlink component carrierother than Pcell.

Control Example 4 With Carrier Aggregation and DFT-S-OFDM Format

In control example 4, as in control example 3, two downlink componentcarriers and one uplink component carrier are configured for terminals200 as illustrated in FIGS. 16A to D. In addition, the DFT-S-OFDM formatis applied as a method of transmitting response signals in terminals200.

Moreover, one of the two downlink component carriers configured forterminals 200 is Pcell (or PCC) and the CCEs included in the PDCCHregion in Pcell are associated in a one-to-one correspondence with PUCCHresources in the uplink component carrier (i.e., PUCCH resources inPUCCH 1 in FIGS. 16A to D) (implicit signaling) as illustrated in FIGS.16A to D.

In control example 4, when previously configuring an R-PDCCH as thedownlink control channel used for transmission of downlink assignmentcontrol information (i.e., DCI) in Pcell, or configuring carrieraggregation for terminals 200, base station 100 previously andexplicitly notifies two specific PUCCH resources including one bundledA/N resource and one A/N resource, together with the result ofconfiguration, for example, using RRC signaling and/or the like(explicit signaling). For example, base station 100 previously andexplicitly notifies the specific PUCCH resources in PUCCH region 2(PUCCH 2) to terminals 200 as a bundled A/N resource and an A/N resourcein FIGS. 16A to D. It should be noted that, the A/N resource is notlimited to the specific PUCCH resource in PUCCH region 2 (PUCCH 2), anda specific PUCCH resource in PUCCH region 1 (not illustrated) may beused as the A/N resource.

In addition, base station 100 maps downlink assignment controlinformation (i.e., DCI) to the PDCCH or R-PDCCH in Pcell and transmitsthe downlink assignment control information (i.e., DCI) to terminals200. Moreover, base station 100 maps downlink assignment controlinformation (i.e., DCI) to the PDCCH in a downlink component carrierother than Pcell and transmits the downlink assignment controlinformation (i.e., DCI) to terminals 200.

Each terminal 200 detects the downlink assignment control information(i.e., DCI) intended for terminal 200 by performing blind-decoding(monitoring) on the PDCCH region and R-PDCCH region at least in Pcell.Terminal 200 (i.e., extraction section 204) extracts downlink data (DLdata) on the basis of the downlink assignment control information mappedto one of the PDCCH and R-PDCCH. In this manner, terminal 200 receivesthe downlink assignment control information and downlink data for eachof the downlink component carriers in at least one of the plurality ofdownlink component carriers.

Subsequently, terminal 200 (i.e., CRC section 211) detects the presenceor absence of an error in receiving the downlink data (DL data) assignedusing the downlink assignment control information (i.e., DCI) intendedfor terminal 200 in each of the downlink component carriers. Inaddition, response signal generating section 212 generates bundledACK/NACK signals or ACK/NACK signals on the basis of the result of errordetection on the downlink data on each of the downlink componentcarriers (i.e., presence or absence of a reception error). Terminal 200transmits the response signals (i.e., ACK/NACK signals or bundledACK/NACK signals) using a PUCCH in the uplink component carrier. Forthis transmission, terminal 200 selects the A/N resource used fortransmission of the response signals according to whether the downlinkassignment control information (i.e., DCI) intended for terminal 200 ismapped to the PDCCH or R-PDCCH in Pcell and also whether or not downlinkassignment control information is assigned to a downlink control channelof each of the downlink component carriers.

To put it more specifically, as illustrated in FIG. 16A, when receivingthe downlink assignment control information intended for terminal 200 onthe PDCCH in Pcell but receiving no downlink assignment controlinformation in the other downlink component carrier (e.g., Scell orSCC), terminal 200 selects the PUCCH resource associated in a one-to-onecorrespondence with the CCE (i.e., PUCCH resource in PUCCH 1) to whichthe downlink assignment control information is mapped (i.e., CCE usedfor transmission of the PDCCH). Terminal 200 transmits the responsesignals (i.e., ACK/NACK signals) for the downlink data (DL data)received in Pcell using the selected PUCCH resource.

In addition, when receiving the downlink assignment control informationintended for terminal 200 on the R-PDCCH in Pcell but receiving nodownlink assignment control information in the other downlink componentcarrier, terminal 200 (i.e., control section 208) selects the A/Nresource previously and explicitly notified by base station 100 asillustrated in FIG. 16B. Terminal 200 transmits the response signals(i.e., ACK/NACK signals) for the downlink data (DL data) received inPcell using the selected A/N resource.

In addition, when receiving the downlink assignment control informationintended for terminal 200 on the PDCCH in Pcell and also receiving thedownlink assignment control information in the other downlink componentcarrier, terminal 200 (i.e., control section 208) selects the bundledA/N resource previously and explicitly notified by base station 100 asillustrated in FIG. 16C. Terminal 200 transmits the bundled A/N signalsobtained by jointly encoding (i.e., joint coding) the response signalsfor the pieces of downlink data (DL data) received respectively in Pcelland in the other downlink component carrier using the selected bundledA/N resource.

In addition, when receiving the downlink assignment control informationintended for terminal 200 on the R-PDCCH in Pcell and also receiving thedownlink assignment control information in the other downlink componentcarrier, terminal 200 (i.e., control section 208) selects the bundledA/N resource previously and explicitly notified by base station 100 asillustrated in FIG. 16D. Terminal 200 transmits the bundled ACK/NACKsignals obtained by jointly encoding the response signals for the piecesof downlink data (DL data) received respectively in Pcell and in theother downlink component carrier using the selected bundled A/Nresource.

In this manner, base station 100 can minimize an increase in the numberof A/N resources to be secured for transmission of ACK/NACK signals forthe downlink data assigned by the downlink assignment controlinformation transmitted via an R-PDCCH, i.e., to minimize an increase inthe overhead of PUCCH resources as in control example 3.

Moreover, although one bundled A/N resource and one A/N resource arepreviously and explicitly notified to terminal 200 by base station 100,it is not true that terminal 200 always uses the bundled A/N resourceand the A/N resource for transmission of response signals. To put itmore specifically, when receiving downlink assignment controlinformation via the PDCCH in Pcell but receiving no downlink assignmentcontrol information in the other downlink component carrier, terminal200 preferentially uses the PUCCH resource associated with the CCE thathas been occupied by the PDCCH used for transmission of the downlinkassignment control information in Pcell. To put it differently, thebundled A/N resource is used in terminals 200 only when necessary. Thus,a plurality of terminals 200 can share the same bundled A/N resource.Thus, base station 100 can control response signals from terminals 200so as to avoid a collision between the response signals from terminals200 while allowing a plurality of terminals 200 to share the samebundled A/N resource through the extremely simple scheduling as in thecase of control example 3, thereby minimizing an increase in theoverhead of PUCCH resources.

Moreover, in control example 3 (FIG. 15B), when receiving the downlinkassignment control information intended for terminal 200 on the R-PDCCHin Pcell, but receiving no downlink assignment control information inthe other downlink component carrier, terminal 200 transmits ACK/NACKsignals using the bundled A/N resource. In other words, an excessiveamount of resources is assigned to the transmission of ACK/NACK signalsin control example 3 (FIG. 15B). In contrast to control example 3,terminal 200 transmits ACK/NACK signals using the A/N resource incontrol example 4 (FIG. 16B). In other words, an appropriate amount ofresources is assigned to the transmission of ACK/NACK signals in controlexample 4. Accordingly, an increase in the overhead of the PUCCHresources can be further minimized compared with control example 3.

Accordingly, in control example 4, a plurality of terminals 200 canshare the same A/N resource and bundled A/N resource whilepreferentially using the PUCCH resource previously associated with theCCE that has been occupied by the PDCCH in Pcell. Thus, the useefficiency of PUCCH resources can be improved with almost no additionallimitations on a scheduler of base station 100. To put it differently,terminal 200 can efficiently transmit response signals even whenreceiving downlink assignment control information via an R-PDCCH in acase where the DFT-S-OFDM format is adopted.

In FIGS. 16A to D, the case where terminal 200 monitors an R-PDCCHregion only in Pcell has been described. However, the operation ofcontrol example 4 can be applied to a case where terminal 200 monitorsan R-PDCCH on a downlink component carrier other than Pcell, i.e., acase where an R-PDCCH is configured in a downlink component carrierother than Pcell.

Control examples 1 to 4 used for transmission of response signals havebeen described above.

As has been described, terminal 200 controls the transmission ofresponse signals by selecting the resource used for transmission of theresponse signals, from the PUCCH resource associated with a CCE and aspecific PUCCH resource previously notified by base station 100,according to whether downlink control information is mapped to a PDCCHor R-PDCCH (whether downlink control information is received on a PDCCHor R-PDCCH). Thus, terminal 200 can selectively use the PUCCH resourceassociated with a CCE and the specific PUCCH resource previouslynotified by base station 100 in accordance with the type of downlinkcontrol channel (i.e., PDCCH or R-PDCCH) or the reception condition ofdownlink control information. Accordingly, even when terminal 200receives downlink assignment control information via an R-PDCCH, anincrease in the number of PUCCH resources to be secured for transmissionof response signals can be minimized while an increase in complexity ofscheduling in base station 100 is also prevented.

In addition, base station 100 selects the resource used for transmissionof response signals, from the PUCCH resource associated with a CCE and aspecific PUCCH resource previously notified to terminal 200, accordingto whether the downlink control information is mapped to a PDCCH orR-PDCCH (i.e., whether the downlink control information is transmittedon the PDCCH or R-PDCCH). Accordingly, when transmitting downlinkassignment control information to terminal 200 using either one of thedownlink control channels, base station 100 can identify which resourceis used for transmission of response signals by terminal 200.

Thus, according to Embodiment 1, terminals can efficiently transmitresponse signals when receiving downlink assignment control informationvia an R-PDCCH.

Embodiment 2

In Embodiment 2, a description will be provided regarding a case where acertain terminal transmits uplink data and response signals for downlinkdata in the same subframe (i.e., the same transmission timing).

The basic configuration of a base station according to Embodiment 2 iscommon to that of Embodiment 1. Accordingly, a description will beherein provided with reference to FIG. 11. Moreover, FIG. 17 is a blockdiagram illustrating the configuration of a terminal according toEmbodiment 2. In terminal 400 illustrated in FIG. 17, the sameconfiguration elements as those illustrated in Embodiment 1 (FIG. 12)are assigned the same reference numerals and any duplicate descriptionof the elements is omitted.

In terminal 400 illustrated in FIG. 17, in addition to the sameprocessing as that in Embodiment 1, control section 208 instructs codingand modulation section 213 to output the response signals that haveundergone coding and modulation to puncturing section 402 when there aredata signals to be transmitted (i.e., transmission data) in a subframeto be used for the transmission of response signals (i.e., bundledACK/NACK signals or ACK/NACK signals). Meanwhile, when there are no datasignals to be transmitted (i.e., transmission data) in a subframe to beused for the transmission of response signals, control section 208instructs coding and modulation section 213 to output the responsesignals that have undergone coding and modulation (i.e., bundledACK/NACK signals or ACK/NACK signals) to DFT section 216 orprimary-spreading section 214-1 as in the case of Embodiment 1.

Coding and modulation section 401 encodes and modulates the transmissiondata and outputs the data signals resulting from coding and modulationto puncturing section 402.

Upon reception of the response signals from coding and modulationsection 213, puncturing section 402 decimates (i.e., punctures) part ofthe data signals received from coding and modulation section 401 andoutputs the signals resulting from the puncturing to DFT section 403.Meanwhile, when receiving no response signals from coding and modulationsection 213, puncturing section 402 outputs the data signals receivedfrom coding and modulation section 401 to DFT section 403 withoutdecimating part of the data signals. As described, when there are datasignals to be transmitted in a subframe to be used for the transmissionof response signals, the response signals are assigned to a PUSCH.

DFT section 403 transforms the signals received from puncturing section402 into frequency-domain signals and outputs the obtained plurality offrequency components to mapping section 404. Mapping section 404 mapsthe plurality of frequency components received from DFT section 403 to aPUSCH assigned in an uplink component carrier. IFFT section 405transforms the plurality of frequency components mapped to the PUSCHinto a time-domain waveform, and CP adding section 406 adds a CP to thetime-domain waveform.

Selection section 407 selects one of the bundled ACK/NACK resourcereceived from time-multiplexing section 220, the A/N resource receivedfrom CP adding section 219-1, and the PUSCH resource received from CPadding section 406 and outputs the signals assigned to the selectedresource to radio transmitting section 222.

(Operations of Base Station 100 and Terminal 400)

A description will be provided regarding operations of base station 100and terminal 400 configured in the manner described above. In thefollowing description, an example of a case without carrier aggregationas in the case of control example 1 of Embodiment 1 will be described.

As illustrated in FIGS. 18A and B, base station 100 according toEmbodiment 2 transmits downlink assignment control information (i.e.,downlink assignment) using a PDCCH region or R-PDCCH region (e.g.,R-PDCCH region in slot 0 illustrated in FIG. 7). In addition, basestation 100 transmits uplink assignment control information (i.e., ULgrant) using a PDCCH region or R-PDCCH region (e.g., R-PDCCH region inslot 1 as illustrated in FIG. 7). Moreover, base station 100 maytransmit uplink assignment control information simultaneously withdownlink assignment control information in a certain subframe toterminal 400.

Meanwhile, terminal 400 performs blind-decoding (monitoring) in both ofthe PDCCH region and R-PDCCH region to detect the downlink assignmentcontrol information or uplink assignment control information intendedfor terminal 400.

During the blind-decoding, when detecting only the downlink assignmentcontrol information intended for terminal 400, terminal 400 transmitsresponse signals using a PUCCH as in the case of control example 1 ofEmbodiment 1. To put it differently, terminal 400 determines theresource used for transmission of response signals (i.e., A/N resource)in accordance with the downlink control channel (i.e., PDCCH or R-PDCCH)used for transmission of the downlink assignment control information.

Meanwhile, when detecting both of the downlink assignment controlinformation and uplink assignment control information intended forterminal 400 in a certain subframe, i.e., when transmitting the uplinkdata and the response signals for the downlink data in the samesubframe, terminal 400 multiplexes the uplink data (Data) and theresponse signals (A/N) in the PUSCH region and transmits the multiplexeddata and signals.

To put it more specifically, as illustrated in FIGS. 18A and B, uponreception of the downlink assignment control information and the uplinkassignment control information in a certain subframe, terminal 400transmits the response signals using the same resource in the PUSCHregion (i.e., PUSCH resources in the PUSCH indicated by the uplinkassignment control information), regardless of whether the downlinkassignment control information intended for terminal 400 is received viathe PDCCH (FIG. 18A) or R-PDCCH (FIG. 18B). In other words, terminal 400transmits response signals using part of the PUSCH resources to whichuplink data (UL data) is assigned (i.e., the part of the uplink data ispunctured due to response signals) as illustrated in FIGS. 18A and B.

As described above, upon reception of only downlink assignment controlinformation (no uplink assignment control information), terminal 400 canimprove the use efficiency of PUCCH resources as in the case ofEmbodiment 1. In addition, upon reception of uplink assignment controlinformation simultaneously with downlink assignment control information,terminal 400 transmits response signals using PUSCH resources withoutusing any PUCCH resource. In this manner, terminal 400 can appropriatelytransmit response signals while reducing the overhead of the PUCCHresources required for transmission of response signals in accordancewith the presence or absence of uplink assignment control information.

According to Embodiment 2, upon reception of downlink assignment controlinformation via an R-PDCCH, terminals can efficiently transmit responsesignals as in the case of Embodiment 1.

Embodiment 2 can be applied not only to control example 1 of Embodiment1, but also to control examples 2 to 4 (where carrier aggregation isemployed).

In other words, when detecting only downlink assignment controlinformation intended for terminal 400, terminal 400 may determine theA/N resource in accordance with one of control examples 1 to 4 ofEmbodiment 1.

Embodiments 1 and 2 of the claimed invention have been described above.

In the above described embodiments, ZAC sequences, Walsh sequences, andDFT sequences are described as examples of the sequences used forspreading. However, instead of ZAC sequences, sequences that can beseparated using different cyclic shift values, other than ZAC sequencesmay be used. For example, the following sequences may be used forprimary-spreading: generalized chirp like (GCL) sequences; constantamplitude zero auto correlation (CAZAC) sequences; zadoff-chu (ZC)sequences; PN sequences such as M sequences or orthogonal Gold codesequences; or sequences having a steep autocorrelation characteristic onthe time axis randomly generated by computer. In addition, instead ofWalsh sequences and DFT sequences, any sequences may be used asorthogonal code sequences as long as the sequences are mutuallyorthogonal or considered to be substantially orthogonal to each other.In the abovementioned description, the resource of response signals(e.g., A/N resource and bundled ACK/NACK resource) is defined by thefrequency position, cyclic shift value of the ZAC sequence and sequencenumber of the orthogonal code sequence.

Moreover, control section 101 of base station 100 is configured tocontrol mapping in such a way that downlink data and the downlinkassignment control information for the downlink data are mapped to thesame downlink component carrier in the embodiments described above, butis not limited to this configuration. To put it differently, even ifdownlink data and the downlink assignment control information for thedownlink data are mapped to different downlink component carriers, thetechnique described in each of the embodiments can be applied as long asthe correspondence between the downlink assignment control informationand the downlink data is clear.

Furthermore, as the processing sequence in terminals, the case whereIFFT transform is performed after the primary-spreading andsecondary-spreading has been described. However, the processing sequencein terminals is not limited to this sequence. As long as IFFT processingis performed after the primary-spreading processing, an equivalentresult can be obtained regardless of the position of thesecondary-spreading processing.

In each of the embodiments, the description has been provided withantennas, but the claimed invention can be applied to antenna ports inthe same manner.

The term “antenna port” refers to a logical antenna including one ormore physical antennas. In other words, the term “antenna port” does notnecessarily refer to a single physical antenna, and may sometimes referto an antenna array including a plurality of antennas, and/or the like.

For example, 3GPP LTE does not specify the number of physical antennasforming an antenna port, but specifies an antenna port as a minimum unitallowing base stations to transmit different reference signals.

In addition, an antenna port may be specified as a minimum unit to bemultiplied by a precoding vector weighting.

The above-noted embodiments have been described by examples of hardwareimplementations, but the claimed invention can be also implemented bysoftware in conjunction with hardware.

In addition, the functional blocks used in the descriptions of theembodiments are typically implemented as LSI devices, which areintegrated circuits. The functional blocks may be formed as individualchips, or a part or all of the functional blocks may be integrated intoa single chip. The term “LSI” is used herein, but the terms “IC,”“system LSI,” “super LSI” or “ultra LSI” may be used as well dependingon the level of integration.

In addition, the circuit integration is not limited to LSI and may beachieved by dedicated circuitry or a general-purpose processor otherthan an LSI. After fabrication of LSI, a field programmable gate array(FPGA), which is programmable, or a reconfigurable processor whichallows reconfiguration of connections and settings of circuit cells inLSI may be used.

Should a circuit integration technology replacing LSI appear as a resultof advancements in semiconductor technology or other technologiesderived from the technology, the functional blocks could be integratedusing such a technology. Another possibility is the application ofbiotechnology and/or the like.

The disclosure of the specification, the drawings, and the abstractincluded in Japanese Patent Application No. 2010-197768, filed on Sep.3, 2010, is incorporated herein by reference in its entirety.

INDUSTRIAL APPLICABILITY

The claimed invention can be applied to mobile communication systemsand/or the like.

REFERENCE SIGNS LIST

-   100 Base station-   101, 208 Control section-   102 Control information generating section-   103 Coding section-   104 Modulation section-   105 Coding section-   106 Data transmission controlling section-   107 Modulation section-   108, 404 Mapping section-   109, 218-1, 218-2, 218-3, 405 IFFT section-   110, 219-1, 219-2, 219-3, 406 CP adding section-   111, 222 Radio transmitting section-   112, 201 Radio receiving section-   113, 202 CP removing section-   114 PUCCH extracting section-   115 Despreading section-   116 Sequence controlling section-   117 Correlation processing section-   118 A/N determining section-   119 Bundled A/N despreading section-   120 IDFT section-   121 Bundled A/N determining section-   122 Retransmission control signal generating section-   200, 400 terminal-   203 FFT section-   204 Extraction section-   205, 209 Demodulation section-   206, 210 Decoding section-   207 Determination section-   211 CRC section-   212 Response signal generating section-   213, 401 Coding and modulation section-   214-1, 214-2 Primary-spreading section-   215-1, 215-2 Secondary-spreading section-   216, 403 DFT section-   217 Spreading section-   220 Time-multiplexing section-   221, 407 Selection section-   402 Puncturing section

1. A terminal comprising: a receiving section that receives downlinkcontrol information via one of a first downlink control channeltransmitted by one or a plurality of control channel elements (CCE)associated with a resource of an uplink control channel and a seconddownlink control channel different from the first downlink controlchannel and that receives a piece of data via a data channel; ageneration section that generates response signals for the piece of dataon the basis of the presence or absence of an error in the piece ofdata; and a control section that controls transmission of the responsesignals by selecting a resource of the uplink control channel used forthe transmission of the response signals, from a resource associatedwith the CCE and a specific resource notified by a base station,according to whether the downlink control information is received viathe first downlink control channel or the second downlink controlchannel.
 2. The terminal according to claim 1, wherein the controlsection selects the resource associated with the CCE used fortransmission of the first downlink control channel, when the downlinkcontrol information is received via the first downlink control channel,and the control section selects the specific resource when the downlinkcontrol information is received via the second downlink control channel.3. The terminal according to claim 1, wherein the specific resourceincludes a first resource and a second resource, the receiving sectionreceives the piece of data on each of a plurality of downlink componentcarriers, the generation section generates the response signals inaccordance with a pattern of the presence or absence of errors in thepieces of data on the respective downlink component carriers, thecontrol section selects the first resource or the resource associatedwith the CCE used for transmission of the first downlink controlchannel, when the downlink control information is received via the firstdownlink control channel, and the control section selects the firstresource or the second resource when the downlink control information isreceived via the second downlink control channel.
 4. The terminalaccording to claim 1, wherein the receiving section receives, on atleast one of a plurality of downlink component carriers, the downlinkcontrol information and the piece of downlink data for each of thedownlink component carriers, the generation section generates theresponse signals on the basis of the presence or absence of an error inthe piece of data for the downlink component carrier on which thedownlink control information is received, the control section selectsthe resource associated with the CCE used for transmission of the firstdownlink control channel when the downlink control information isreceived via the first downlink control channel on a specific downlinkcomponent carrier paired with an uplink component carrier to be used fortransmission of the response signals while the downlink controlinformation is not received on another downlink component carrier otherthan the specific downlink component carrier among the plurality ofdownlink component carriers, and the control section selects thespecific resource when the downlink control information is received viathe second downlink control channel on the specific downlink componentcarrier while the downlink control information is not received on theother downlink component carrier among the plurality of downlinkcomponent carriers.
 5. The terminal according to claim 4, wherein thecontrol section selects the specific resource when the downlink controlinformation is received on the specific downlink component carrier whilethe downlink control information is received on the other downlinkcomponent carrier among the plurality of downlink component carriers. 6.The terminal according to claim 1, wherein when the downlink controlinformation and uplink control information are received in the sametransmission time interval, the control section further selects a partof resources in an uplink data channel indicated by the uplink controlinformation.
 7. A base station comprising: a transmitting section thattransmits downlink control information via one of a first downlinkcontrol channel transmitted by one or a plurality of control channelelements (CCE) associated with a resource of an uplink control channeland a second downlink control channel different from the first downlinkcontrol channel and that transmits a piece of data via a data channel;and a receiving section that selects a resource used for transmission ofresponse signals for the piece of data in a terminal, from a resourceassociated with the CCE and a specific resource notified to theterminal, according to whether the transmitting section has transmittedthe downlink control information via the first downlink control channelor the second downlink control channel and that receives the responsesignals using the selected resource.
 8. A signal transmission controlmethod comprising: receiving downlink control information via one of afirst downlink control channel associated with a resource of an uplinkcontrol channel and a second downlink control channel different from thefirst downlink control channel, and also receiving a piece of data via adata channel; generating response signals for the piece of data on thebasis of the presence or absence of an error in the piece of data; andcontrolling transmission of the response signals by selecting a resourceof the uplink control channel used for the transmission of the responsesignals, from a resource associated with control channel elements (CCE)and a specific resource notified by a base station, according to whetherthe downlink control information is received via the first downlinkcontrol channel or the second downlink control channel.